The US Navy said Wednesday that the super carrier USS Nimitz, escorted by a covering screen of cruisers, destroyers and submarines, has entered the western Pacific, joining the Roosevelt and Reagan carrier strike groups already deployed in the region.

The move places three powerful US carrier groups within striking distance of North Korea ahead of a 12-day visit to Asia next month by President Donald Trump.

The nuclear-armed carriers, with their tactical air wings, are now part of the US 7th Fleet area of operations which covers the eastern Indian and western Pacific oceans.

The San Diego-based USS Theodore Roosevelt arrived in the western Pacific earlier this week. It is accompanied by the guided-missile cruiser USS Bunker Hill and guided-missile destroyers.

The Japan-based USS Ronald Reagan carrier strike group arrived off South Korea’s port city of Busan for a five-day maritime exercise with the South Korean Navy last week. The maneuvers have ended and the Reagan is officially scheduled to return to its homeport of Yokosuka on Saturday.

The US has substantially bolstered its forces in the region amid tensions with North Korea over its nuclear weapons and missile programs. The US Air Force said Tuesday that it will deploy a dozen F-35A Lightning stealth fighters to Japan next month.