Chinese warships will join US-led naval drills off Hawaii for the first time this week, in a significant but mainly symbolic effort by the two powers' fighting forces to make friends, not war.

Rising giant China and superpower the United States frequently find themselves at loggerheads as Beijing asserts itself in maritime disputes with neighbours and Washington seeks to shore up its influence in Asia.

Forging friendly ties -- or at least an understanding -- between the two heavyweights' militaries is a key to preventing any unintended clashes from escalating, analysts say.

Yet "mil-to-mil" ties remain stunted by disputes and suspicions which have sharpened in recent years as each side accuses the other of inflaming tensions over contested islands in the East and South China Seas, aggressive cyber-spying and other issues.

"It's pretty important," said Michael O'Hanlon, a senior fellow at the US-based Brookings Institution and author of a book on US-China relations.

"We have a situation where small crises or skirmishes blowing up into bigger things is one of our chief worries, and a situation where US-PLA ties at the military level are underdeveloped."

Four ships of the People's Liberation Army Navy with an estimated 1,100 sailors on board -- a missile destroyer, missile frigate, supply ship and hospital ship -- will join the US and more than 20 other countries in the six-day "Rim of the Pacific" drills that begin in and around Hawaii Thursday.

The RIMPAC exercises, normally held every two years, began in 1971 but it is the first time Chinese vessels have taken part.

The head of US Pacific Command, Admiral Samuel Locklear, said: "This was a big step for the Chinese to commit to this, particularly in an exercise commanded by a US commander.

"We just have to get past these issues that are historical in nature that are causing the region problems," he added. "And if we keep working at it we'll get through them."

Beijing has also touted its participation, with the official Xinhua news agency running an essay by naval academy researcher Zhang Junshe saying it "will have great benefits for the elimination of misunderstandings, the avoidance of misjudgment, and the promotion of mutual trust".

China's involvement marks "a very good step", O'Hanlon said in an email. "In isolation it doesn't do a great deal of course, but it provides the basis for more."

- 'Lowest point' -

Beijing and Washington regularly pledge to strengthen ties across the board, and Presidents Xi Jinping and Barack Obama held an informal get-to-know-you summit in California soon after the Chinese leader took office last year.

Both militaries have extended other invitations, including tours of one another's aircraft carriers and high-level meetings.

But despite the positive rhetoric, tensions have grown -- particularly over their roles in Asia -- and spilled into unusual public confrontations.

China has emphatically asserted its claims to islands claimed or controlled by Japan, Vietnam and the Philippines, and desires greater global stature, stressing that its standing with the US must reflect a "new model of great-power relations".

Washington announced a "pivot" to Asia in 2011, including a stronger military presence, with Obama declaring that his country "has been and always will be a Pacific nation".

At the Shangri-La Dialogue security summit in Singapore a month ago, US Defense Secretary Chuck Hagel accused Beijing of "destabilising" actions while China's army deputy chief of staff Wang Guanzhong criticised his words as "full of incitement, threats, intimidation" and the US as "stoking fires".

Cyber-spying is another flashpoint for angry rhetoric, with both sides casting the other as the aggressor.

"You have had a series of incidents that make people pessimistic about the relationship," said Peking University international relations professor Jia Qingguo.

"At the moment the relationship is at a relative low," he said. "I don't know if it has reached the lowest point yet."

- 'Weakest link' -

Mil-to-mil contacts between the two have been on-again, off-again for decades. The US suspended them for four years after China's 1989 crackdown on Tiananmen Square pro-democracy protesters.

Since they they have faltered under other crises, including in 1995-96 when China conducted missile exercises directed at Taiwan, in 1999 when NATO bombed China's embassy in Belgrade, and in 2001 when a US spy plane and Chinese fighter jet collided over the South China Sea.

The "mil-mil relationship is the weakest link between the two countries and they often got suspended whenever something happened", Jia said.

"The militaries need to talk to each other more often and at greater depth."

But both sides increasingly recognise the need to improve ties despite disagreements, said Jingdong Yuan, an Asia-Pacific security expert at the University of Sydney.

A crucial step would be for the militaries to come up with protocols to prevent an unintended conflict from spiralling, he added.

"They both I think are coming to realise that mutual trust is both imperative but also very challenging to build," he said.