Upcoming US and South Korean naval exercises will send "a strong signal" of deterrence to North Korea but the North will pose a continuing challenge in coming years, the US defense secretary said Tuesday.

Robert Gates, visiting the South in a show of support after the sinking of a South Korean warship, said a first joint drill this month would involve 10 US ships including an aircraft carrier, eight South Korean vessels and a large number of aircraft.

During a visit to US troops at Camp Casey north of Seoul, the defense secretary also announced that he and Secretary of State Hillary Clinton would Wednesday visit the Demilitarised Zone (DMZ) separating the two Koreas.

South Korea, the United States and other nations, citing findings of a multinational investigation, accuse the North of sending a submarine to torpedo the warship near the tense Yellow Sea border in March.

The North denies involvement in the sinking, which claimed 46 lives, and says any retaliation could spark war.

It says it was vindicated by a United Nations Security Council statement on July 9 that condemned the attack without specifying the culprit.

Gates described the statement as "pretty clear and pretty firm" in its condemnation. The communist North's missile and nuclear proliferation pose a serious challenge, he added.

"This is an ongoing challenge that has to be managed over a period of years" but "I think that the pressure continues to slowly build on the North."

The United States, which stations 28,500 troops in the South, and South Korea are pressing ahead with war games despite strong protests from the North's ally China.

But Seoul's defence ministry has said this month's drill has been partially relocated from the sensitive Yellow Sea (West Sea) to the Sea of Japan (East Sea) in deference to Chinese concerns.

More details of the drill, the first in a series, were expected to be announced later Tuesday after Gates meets Defence Minister Kim Tae-Young.

The exercises were "designed to enhance our interoperability and readiness, but are also a strong signal of deterrence to the North," Gates said, adding they would practise anti-submarine drills and air operations.

He declined to say whether this month's exercise involving the carrier the USS George Washington would be held in the Yellow Sea, but insisted the drills are not intended to provoke China.

"There should be no doubt in anybody's minds that we intend to exercise in both seas," Gates said.

The top US military officer, Admiral Mike Mullen, made a similar point.

"The Yellow Sea specifically is an international body of water and the United States has always reserved the right to operate in those international waters," the chairman of the Joint Chiefs of Staff told reporters on his plane bound for Seoul.

"I hear what the Chinese are saying with respect to that, but in fact we have exercised in the Yellow Sea for a long time. And I fully expect we will do so in the future."

Gates said Wednesday's visit to the DMZ was designed to "highlight how important operations are there to the security of the peninsula as well as to the region, and demonstrate our steadfast commitment to the Republic of Korea (South Korea)."

Gates will meet defence minister Kim again Wednesday, while Clinton will hold talks with Foreign Minister Yu Myung-Hwan.

The "Two Plus Two" meeting, the first of its kind, was arranged to mark the 60th anniversary of the start of the Korean War in which a US-led United Nations force defended the South.

earlier related report
US military chief defends naval exercises
Aboard A Us Military Aircraft (AFP) July 20, 2010 - The top US military officer Admiral Mike Mullen on Tuesday defended plans for joint US-South Korean naval exercises in the Yellow Sea, despite protests from China.

The drills with the South Korean military are designed to reaffirm the alliance and deliver a warning to North Korea after the sinking of a South Korean warship in March, Mullen said.

"Certainly the intent of those exercises, as clearly stated, is to focus on stability on the (Korean) peninsula. It is not intended one way or another to send the Chinese a message," Mullen told reporters on his plane bound for Seoul.

"We exercise with the Koreans routinely in this part of the world and have for decades."

South Korea, the United States and other nations, citing the findings of a multinational investigation, accuse the North of torpedoing the warship near the tense Yellow Sea border.

Pyongyang denies involvement and Beijing has refused to blame its ally.

China has expressed concern about American warships carrying out exercises in the Yellow Sea between its coast and the Korean peninsula.

But Mullen said the US Navy would continue to operate in the region.

"The Yellow Sea specifically is an international body of water and the United States has always reserved the right to operate in those international waters," said Mullen, chairman of the Joint Chiefs of Staff.

"I hear what the Chinese are saying with respect to that, but in fact we have exercised in the Yellow Sea for a long time. And I fully expect we will do so in the future."

Details of an upcoming drill and of others scheduled later this year were expected to be announced later Tuesday.

But Seoul's defence ministry has said the upcoming exercise has been partially relocated from the sensitive Yellow Sea to the Sea of Japan (East Sea) in deference to Chinese concerns.

China's misgivings are the latest sign of strains with Washington.

US officials have been frustrated at Beijing's reluctance to back punitive measures against Pyongyang, as well as its decision earlier this year to suspend military contacts with the US armed forces.

China cut off military relations after Washington unveiled plans for 6.4 billion dollars in arms sales for Taiwan. It called off a planned visit to Beijing in June by US Defense Secretary Robert Gates.

Mullen said he hoped China and the United States could resume military relations in the future, saying such contacts were crucial to reducing tensions.

"I think that's very important, in terms of our ability to understand each other, deal with the tough issues, agree in certain areas and disagree in others. But at least having those conversations is vital," he said.

Mullen travelled to Seoul as part of high-level talks between the United States and South Korea, featuring a joint meeting on Wednesday of the two governments' top diplomats and defence chiefs.

The four-star admiral said the talks underlined the importance of the US alliance with South Korea, underscoring "regional strength" and unity in the face of the threat posed by North Korea.

The anti-submarine exercises carried tactical importance but were also meant to "send a message to the North Koreans that their behaviour is completely counter to international norms, completely unacceptable".

Mullen was due to visit some of the 28,500 troops stationed in South Korea, part of a US military presence dating back to the 1950-53 Korean War.

earlier related report
ASEAN meets in shadow of Korea tensions
Hanoi (AFP) July 20, 2010 - Southeast Asian foreign ministers met in Vietnam on Tuesday for discussions dominated by concerns over the sinking of a South Korean warship and elections in military-ruled Myanmar.

Ministers from the Association of Southeast Asian Nations (ASEAN) are meeting in Hanoi ahead of the region's main security forum Friday, which also gathers major powers including China, the United States and the European Union.

A draft statement prepared ahead of Tuesday's talks said the 10 ASEAN member states supported a nuclear-free Korean peninsula and urged a resumption of six-party disarmament talks "as soon as possible".

"We deplored the incident of the Cheonan ship sinking and the rising tension on the Korean peninsula," the draft statement said, referring to an explosion that ripped apart a South Korean warship in March, killing 46 sailors.

It said the six-party talks involving North and South Korea, the United States, China, Japan and Russia were still the "main platform to achieve long-lasting peace and stability".

US Secretary of State Hillary Clinton and North Korean Foreign Minister Pak Ui-Chun will attend the 27-member ARF meeting alongside their counterparts from the six-party process.

It will be the first time the top diplomats from the disarmament dialogue will be in the same room since the Cheonan incident dramatically raised tensions on the Korean peninsula.

ASEAN chief Surin Pitsuwan said it was an opportunity to "engage in a discussion to see if the six-party talks can be given a new life".

Clinton will arrive in Vietnam after visits this week to Pakistan and South Korea, where she is due to attend a memorial for the dead sailors and visit the Demilitarised Zone (DMZ) alongside Defense Secretary Robert Gates.

South Korea, the United States and other nations, citing the findings of a multinational investigation, accuse the North of firing a torpedo that sank the warship.

The North vehemently denies the allegations and has warned that any attempts to punish it could trigger war.

But the country has also said it is willing to return to the multilateral disarmament talks, which it abandoned last year, after the United Nations Security Council on July 9 condemned the sinking but did not assign blame.

The United States, which has 28,500 troops in the South, has expressed skepticism about the North's sincerity and responded by announcing plans to hold naval exercises with South Korea starting on July 25.

A US aircraft carrier, the 97,000-tonne USS George Washington, and three destroyers will visit South Korea this week ahead of the exercise.

During a visit to US troops north of Seoul on Tuesday, Gates said the drills were "a strong signal of deterrence to the North" but were not intended to provoke China, Pyongyang's strongest ally.

A draft ARF chairman's statement suggests the security forum is likely to follow ASEAN's lead by expressing concern about the situation on the Korean peninsula without explicitly condemning the North for the Cheonan incident.

South Korean Foreign Minister Yu Myung-hwan wants some form of direct condemnation of the North to be included in the final statement, and would oppose any declaration that includes Pyongyang's denials.

On Myanmar, the draft ASEAN statement calls for free and fair elections in the military-ruled member state and the involvement of "all parties".

Nobel peace laureate Aung San Suu Kyi's opposition party has opted to boycott the vote -- due some time this year -- because of rules that would have forced it to expel its leader.

Surin said Myanmar Foreign Minister Nyan Win "got an earful" from his ASEAN colleagues on the need for a credible vote.

Myanmar's top diplomat "listened very, very attentively" during the discussions late Monday, Surin added.

The bloc of almost 600 million people -- grouping Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam -- maintains a policy of non-interference in members' affairs.