TOKYO - Two U.S. aircraft carriers with around 150 fighter jets are conducting "complex" warfare drills in the Philippine Sea, the U.S. Navy said on Thursday, in a show of force in waters south of China and within striking distance of North Korea.

The two carriers, the Japan-based USS Ronald Reagan and the USS John C Stennis deployed from the U.S. West coast, are carrying out air, surface and anti-submarine warfare operations, the U.S. Seventh Fleet said in a news release.

The U.S. Navy has conducted such operations before, including drills by three carriers last year as tensions with North Korea escalated. The latest, which coincides with U.S. Vice President Mike Pence's visit to the region, comes as denuclearization talks with North Korea show little sign of progress and amid a tit-for-tat trade spat with China.

"Bringing two carrier strike groups together provides unparalleled naval combat power," U.S. Seventh Fleet commander Vice Admiral Phil Sawyer said.

The USS Reagan also took part in the biggest war games ever staged in and around Japan this month, involving dozens of U.S. and Japanese ships, hundreds of aircraft and thousands of military personnel.