The U.S. Navy aircraft carrier, Carl Vinson, previously scheduled for a port call in Australia has reversed course — and currently is heading back to waters off the Korean peninsula following recent provocations from North Korea.

The carrier group includes the aircraft carrier USS Carl Vinson, with support from several missile destroyers and missile cruisers.

Last month, the USS Carl Vinson strike group had participated in annual military exercises with the South Korean military — that North Korea regards as rehearsal for invasion. In a show of defiance, North Korea fired four ballistic missiles into the ocean off Japan last month. Shortly thereafter, the U.S. began bringing in equipment for the long-planned deployment in South Korea of a missile defense system, known as THAAD.

The Pentagon continues to see signs North Korea is preparing for another nuclear test, following two last year. Officials are concerned that the country could one day place a nuclear weapon atop a missile, which could reach the United States.

On Saturday, President Donald Trump and South Korea's leader, acting President Hwang Kyo-Ahn, spoke by phone. The White House said the two agreed to stay in close contact about North Korea and other issues.

The U.S. Pacific Command directed the carrier group to sail north to the western Pacific after departing Singapore on Saturday, according to a Navy news release.

April 15 is the 105th birthday of North Korea’s founding president, and considered the biggest holiday of the year in Pyongyang.

North Korea has launched a number of ballistic missiles recently into waters off Japan, sparking international outrage.

This week, President Tump hosted Chinese President Xi Jinping at Mar-a-Lago in Florida, where North Korea was expected to be at the top of the agenda, before Trump ordered 59 Tomahawk cruise missiles into Syria.

Fox News' Lucas Tomlinson and the Associated Press contributed to this report.

