The United States is conducting two military exercises in Asian waters this week involving allies Japan, Australia and India, the US navy said yesterday.

The exercises come as military rivalry between the United States and China is intensifying and days after the United States said China's claims of sovereignty in the disputed South China Sea were illegal. It also comes after deadly clashes between Indian and Chinese forces in Ladakh last month. 

The USS Nimitz and the USS Ronald Reagan were deployed to the South China Sea twice this month but this week, the Nimitz was in the Indian Ocean for exercises with the Indian navy, the US navy said, in the latest sign of growing cooperation between the forces.

Rear Admiral Jim Kirk, commander of the Nimitz Carrier Strike Group, said in a statement that Monday's drills with the Indian navy helped improve the interoperability of their forces. The drills were carried out near India's Andaman and Nicobar islands, off the north end of the Malacca Straits, one of the world's busiest shipping routes for trade and fuel, an Indian source said.

Separately, the US strike group led by the Ronald Reagan was carrying out drills with naval forces from Japan and Australia in the Philippine Sea, US and Australian officials said yesterday. The exercises are due to end on July 23, Australia's defence department said.