US Defense Secretary Lloyd Austin has said he is deeply concerned by China's reluctance to engage in military crisis management, warning that talks are key to avoiding conflict. Reuters.

The relationship between the US and China is at its lowest level in decades as they remain deeply divided over everything from Taiwan sovereignty to espionage and territorial disputes in the South China Sea.

Speaking at the Shangri-La Dialogue, Asia's top security summit, Austin said open lines of communication between US and Chinese defense and military leaders are essential to avoid conflict and enhance stability in the Asia-Pacific.

"I am deeply concerned that China has been reluctant to engage more seriously in better crisis management mechanisms between our two militaries," Austin said at the meeting in Singapore.

Chinese National Defense Minister Li Shangfu this week declined an invitation to meet with Austin at a security summit. Lee, a US-sanctioned general, will deliver his speech on Sunday.

On Friday, the two shook hands on the sidelines of the conference but did not hold detailed talks, the Pentagon said.

"A cordial handshake over dinner is no substitute for substantive engagement," Austin said.

Dialogue between the two countries has stalled since US Secretary of State Anthony Blinken canceled a visit to China in February after a suspected Chinese spy balloon was tracked flying over the United States.

Liu Pengyu, a spokesman for the Chinese embassy in Washington, said in an emailed statement on Friday that communication between China and the US is conducive to greater mutual understanding.