Four former US defense secretaries believe that China and the United States should increase military-to-military exchanges.

Asked on Monday by Stephen Orlins, president of the National Committee on US-China Relations (NCUSCR) whether US military academies such as West Point should accept Chinese cadets, they all said yes.

The four ex-Pentagon chiefs- Harold Brown, William Perry, William Cohen and Chuck Hagel - were attending the first session of the Leaders Speak Series, kicked off by the NCUSCR to celebrate the 50th anniversary of its founding.

Brown, who served as defense secretary from 1977 to 1981 under President Jimmy Carter, said "we should do more to encourage military-to-military relationship at the senior level".

Perry, who served under President Bill Clinton from 1994 to 1997, agreed. He added that the US Pacific Command has a special role to play, given its close ties with the Chinese military, such as sponsoring ship visits.

Cohen, who was defense secretary from 1997 to 2001, also under Clinton, believes the US should include the Chinese military more in some of its exercises so it does not look like just the US, Australia and Japan conducting exercises that appear to be aimed at the Chinese.

"That's the way of trying to build more trust even though that might raise some questions about security," he said.

The US Congress has passed the National Defense Authorization Act restricting military-to-military cooperation with China.

Hagel, who just stepped down last year, said there are many things that "our military leaders have done and are doing to build that military-to-military relationship that most people never see".

"By the way, we are doing more and more military exercises, training with the Chinese," he added.

The four men agreed that the US will continue to deepen the relationship due to common interests in international trade, regional security and prevention of nuclear proliferation.

"The US-China relationship is the most important bilateral relationship, especially from a long-term perspective," Brown said. "The US should take its time and be patient when thinking over foreign policies towards China."

The stable relationship is attributed to deep trade relationships, according to Hagel.

All the former defense secretaries addressed the latest nuclear test in North Korea as the most urgent security issue that China and the US should work on together.

"There would be little progress in the negotiation without China," Perry said. "The US needs China to step up negotiation with North Korea, which is a very dangerous nuclear threat to China, given its geopolitical position."

Perry believes China could take advantage of the close relationship with North Korea to advance Six-Party Talks.

Because of the ambiguous interpretation of international law over the South China Sea, there are some disagreements between China and the US. However, China and the US should have more open dialogue and interaction to surmount the obstacles, Perry said.

When asked to comment on China building a second aircraft carrier, Hagel, who was the only Pentagon boss to visit China's first aircraft carrier Liaoning, said: "I'm not surprised they made that decision.

"I think it is just what China needs to increase their military power," he said. "And it is a symbol that demonstrates China's defense ability."

Hagel concluded the discussion with one word: "listen", hoping the US government listens to its military more and pays more attention to military-to-military exchanges between China and the US.

Pan Jialiang in Washington contributed to this story.