Two US aircraft carriers with around 150 fighter jets are staging warfare drills in west Pacific, the US Navy said on Thursday.

The US Seventh Fleet said the two carriers, the Japan-based USS Ronald Reagan and the USS John C. Stennis, deployed from the West coast of the United States, are carrying out air, surface and antisubmarine warfare operations.

The operations are being conducted in waters south of China and within the striking distance of Democratic People's Republic of Korea.

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

The US Navy has staged such operations before, including drills conducted by three carriers when tensions with DPRK escalated last year.

The latest, which coincides with US Vice-President Mike Pence's visit to the region, comes as the US denuclearization talks with DPRK being stuck in an impasse.

Xu Liping, a senior fellow at the Chinese Academy of Social Sciences, said that US has regular warfare drills, but the timing is usually worth pondering.

He said security issues have been focused on East Asia recently, and the warfare drills are just for the US to show its influence in the region.

"The drill won't have much real impact," he said. "It is just the US wants to tell the world that it may still have some say in the security order in Asia," he said.

He added that the denuclearization talks with the DPRK still have a long way to go, and the US-China trade tension will be eased only when both sides talk with a win-win approach.

The first DPRK-US summit was held in Singapore on June 12. A joint statement signed by DPRK's top leader Kim Jongun and US President Donald Trump said that the US would provide security guarantees to the DPRK in return for Pyongyang's commitment to denuclearization.

However, there is little sign of progress in the talks due to differences over the scale of denuclearization, US sanctions, and whether to issue a war-ending declaration.

Chen Yingqun, Reuters and Xinhua contributed to this story.