Randall Schriver, the Pentagon's assistant secretary of defence for Asian and Pacific Security Affairs, said Defence Secretary Jim Mattis is set to meet his Chinese counterpart General Wei Fenghe in Singapore on Thursday at a regional security summit.

A meeting between the two men had initially been scheduled to take place in Beijing last weekend, but it fell through after China declined to make Wei available.

"I think the fact that (Mattis is now) meeting with Minister Wei is some evidence that the Chinese are interested in keeping things normal and stable -- as are we," Schriver told reporters travelling with Mattis.

"What we have heard in our dialogue is the Chinese are interested in having a military relationship that's a stabilising force in the overall relationship."

China reacted angrily after Washington last month imposed sanctions following Beijing's purchase of Russian fighter jets and missiles, and a close encounter between warships in the South China Sea raised the spectre of a military mishap between the two nuclear powers.

Beijing's actions, which followed the imposition of the sanctions, included scrapping a planned port visit of a US warship to Hong Kong and cancelling a meeting between the head of the Chinese navy and his American counterpart.

Defence ministers from the Association of Southeast Asian Nations (ASEAN) are meeting in Singapore to discuss a range of regional security concerns.

Front and centre is China's military build-up in the South China Sea and its sweeping claims of sovereignty across the economically vital waters.

In an incident the Pentagon decried as "unsafe and unprofessional", a Chinese warship last month sailed within just 45 yards (41 meters) of a US destroyer as it passed by Beijing-claimed features in the South China Sea, forcing the American vessel to take evasive action.

The US periodically conducts such "freedom of navigation" operations to challenge China's claims over international waters.

Schriver said Mattis would be encouraging other countries in the region to assert a presence in the areas which Beijing claims.

"Our message will be no single country can change international law, international norms," he said.

"We will fly sail and operate where international law allows but we are also looking for partners to give voice to keeping ... international law ... upheld."

Still, he stressed the importance of maintaining clear communication with the Chinese military.

"We need to make sure that when we step on one another's toes it doesn't escalate into something that would be catastrophic," he said.