South Korea and the United States on Thursday warned Pyongyang against a potential missile test that they said would be a violation of UN resolutions as the two countries wrapped up annual high-level defence talks.

There has been widespread speculation that North Korea is planning a satellite rocket launch to mark the 70th anniversary of the ruling Workers' Party on October 10.

Senior defense officials who attended the two-day Korea-US Integrated Defense Dialogue vowed to closely coordinate with each other against "potential provocations by the North", Seoul's defense ministry said in a statement.

"The US and South Korean officials... also reaffirmed their stance that any missile launch by the North using ballistic missile technology would be a violation of many UN Security Council resolutions," the statement said.

They also reiterated the stance that the isolated North should dismantle its nuclear weapons programmes in a complete, verifiable and irreversible manner, said the ministry.

Pyongyang insists its space programme is purely scientific, but the US, the South and their allies deem any such rocket launch to be a disguised ballistic missile test that violates UN resolutions.

Tensions rose further after the North last week confirmed the restarting of a nuclear reactor seen as its main source of weapons-grade plutonium.

The confirmation by the head of the North's Atomic Energy Institute came a day after the director of Pyongyang's aerospace development agency strongly hinted at another rocket launch.

The North's only successful satellite launch was of its Unha-3 rocket in December 2012, triggering fresh UN sanctions and a surge in military tension that culminated two months later in its third nuclear test.

The White House has already warned Pyongyang to refrain from any "irresponsible provocation" that might aggravate regional tension.