US warships have been deployed to the western Pacific Ocean to provide a 'physical presence' near the Korean peninsula.
North Korea's recent ballistic missile tests and continued pursuit of a nuclear programme have raised tensions in the region, where US navy ships are a common presence and serve in part as a show of force.
President Trump and South Korea's leader, acting president Hwang Kyo-Ahn, spoke by phone on Saturday and the White House said the two agreed to stay in close contact about North Korea and other issues.
The US Pacific Command directed the carrier group to sail north to the western Pacific after departing Singapore on Saturday.
The group includes the aircraft carrier USS Carl Vinson, with support from several missile destroyers and missile cruisers.
Deployed from San Diego to the western Pacific since January 5, the strike group has participated in numerous exercises with the Japan Maritime Self Defence Force and Republic of Korea Navy, various maritime security initiatives, and routine patrol operations in the South China Sea.