The United States and its Asian allies have expressed growing concern about China's increasing assertiveness in the Pacific, but Washington said the drills were not aimed at any nation even though they were larger than previous training missions.

The exercise in Indonesia known as "Super Garuda Shield" came after Beijing staged unprecedented war games around Taiwan, which it claims as part of its territory, last week in a furious reaction to US House Speaker Nancy Pelosi's visit to the self-ruled democracy.

"The destabilising actions of the People's Republic of China as applied to the threatening activities and actions against Taiwan is exactly what we are trying to avoid," Admiral John Aquilino, head of the US Indo-Pacific Command, told a press conference after the drill.

China's week-long air and sea exercises pushed tensions in the region to their highest level in years and raised the spectre of conflict in the Taiwan Strait.

"Everyday we are trying to prevent war," said Aquilino.

At least 4,000 American and Indonesian soldiers were joined in the two-week exercise by forces from Australia and Singapore -- as well as Japan, which is participating for the first time in the annual drills.

In Friday's drill, only Australian and Singaporean forces joined the US and Indonesian troops.

Joint military forces fired Javelin anti-tank missiles while Apache helicopters staged manoeuvres, shooting rounds of machine gun fire and rockets into a hilly training area.

Indonesian army chief Andika Perkasa denied the expansion of the exercise was due to the situation in the Taiwan Strait, saying the drills had been planned long before that.

Aquilino, echoing Perkasa, said the annual exercises with other countries "continue to become more free-flowing and complex because all the nations in the region are getting better".

Canada, France, India, Malaysia, South Korea, Papua New Guinea, East Timor, and Britain participated in the exercise as observer nations.