The Chinese military has become significantly more aggressive and dangerous over the past five years, a top US military officer has said while visiting Indonesia as part of a trip to the Indo-Pacific.

Chairman of the Joint Chiefs of Staff Mark Milley said the number of intercepts by Chinese aircraft and ships in the Pacific region with US and other partner forces had increased significantly, as had the number of unsafe interactions.

"The message is the Chinese military, in the air and at sea, have become significantly more and noticeably more aggressive in this particular region," General Milley said.

His comments come as the US redoubles efforts to strengthen its relationships with Pacific nations as a counterbalance to China, which is trying to expand its presence and influence in the region.

The Biden administration considers China its "pacing threat," and America's primary long-term security challenge.

In one incident, a Chinese navy ship directed a laser at an Australian patrol aircraft. In another, a surveillance aircraft controlled by Canada was intercepted by a Chinese fighter jet in international airspace.

US ships are routinely dogged by Chinese aircraft and vessels during transits, particularly around man-made islands claimed by Beijing in the South China Sea.

Meeting with his Indonesian counterpart, Chief of the Indonesian National Defence Forces Andika Perkasa, General Milley said nations like Indonesia wanted the US military involved and engaged in the region.

"We want to work with them to develop interoperability and modernise our militaries collectively," he said, to ensure that they could "meet whatever challenge that China poses."

He said Indonesia was strategically critical to the region and had long been a key US partner.

Separately, China's Foreign Minister Wang Yi told a virtual function on Monday that the South China Sea was not a "safari park" for countries outside the region or a "fighting arena" for major powers to compete in.

The South China Sea issue should be handled by countries in the region themselves, Mr Wang said in opening remarks at a virtual seminar commemorating the 20th anniversary of the signing of the Declaration on the Conduct of Parties in the South China Sea.

The declaration was signed by the members of ASEAN and China in 2002. 

General Milley, who spent the afternoon at General Andika's military headquarters, was greeted with a massive billboard bearing his photo and name, a military parade, and a large television screen that showed a video of his career.

At the end of the visit, General Andika told reporters that Indonesia had found China to be more assertive and "a little bit aggressive" with naval vessels in connection with territorial disputes with his country.

Earlier this year, the US approved a $20 billion ($US13.9 billion) sale of advanced fighter jets to Indonesia, and last December it signed agreements for enhanced joint naval exercises between the two nations.

General Milley's visit to Indonesia is the first by a US Joint Chiefs chairman since 2008.

China has condemned US efforts to expand its outreach in the region, accusing America of trying to build an "Asian NATO".

The US General's trip to the region is sharply focused on the China threat, with plans to attend a meeting of Indo-Pacific chiefs of defence in Australia, where key topics will be China's escalating military growth and the need to maintain security in the Pacific.

ABC/AP