Indonesia and the US began a two-week joint military exercise on Monday that Washington announced aims to advance "regional cooperation in support of a free and open" Asia-Pacific region. 

Asian and US allies expressed concern about China's "increasing assertiveness in the Pacific," but Washington claimed that the drills "were not aimed at any country" even though they would be significantly larger than previous exercises. 

At least 4,000 US and Indonesian soldiers will be joined by forces from Australia and Singapore, as well as Japan, which is taking part in the yearly training for the first time.

The drill is taking place in Sumatra, an Indonesian island in western Indonesia, and the Riau islands, an Indonesian province of islets near Singapore and Malaysia.

"This is really an exercise to build trust, build togetherness, mutual understanding, increase capability and other related matters," Major General Stephen Smith, commander of the participating US troops, told reporters in Jakarta on Friday. "So this is really a military exercise and not a threat to any party."

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Pelosi leaves for Asia 

The exercise comes in light of the US House of Representatives Speaker Nancy Pelosi's visit to Asia amid diplomatic tensions with China. 

However, her office did not confirm whether she would visit Taiwan, a flashpoint in negotiations between Beijing and Washington ahead of the trip, which started on Monday.

US President Joe Biden and Chinese President Xi Jinping held a heated phone call on Thursday, agreeing to schedule their first in-person summit, and Xi warned Washington not to "play with fire" in Taiwan.

The exercise, which includes army, navy, air force, and marine maneuvers, will go until August 14. An opening ceremony with all participating nations will take place on Wednesday, an Indonesian official said.

Canada, France, India, Malaysia, South Korea, Papua New Guinea, East Timor, and Britain will participate as observer nations.

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