WASHINGTON - US President Donald Trump on Tuesday announced he was replacing Secretary of State Rex Tillerson with Mike Pompeo, chief of the Central Intelligence Agency (CIA).

Trump tweeted that Pompeo "will do a fantastic job," adding that Gina Haspel, Pompeo's deputy, will become the new director of the CIA as "the first woman so chosen."

Nikki Haley, US ambassador to the United Nations, tweeted that the replacement was a "great decision by the President." She also congratulated Pompeo on the new nomination, calling him a "friend."

According to a statement offered by White House spokesperson Sarah Sanders, Trump said Pompeo, who "graduated first in his class at West Point, served with distinction in the US army" and praised him for having served in the House of Representatives "with a proven record of working across the aisle."

"I have gotten to know Mike very well over the past 14 months, and I am confident he is the right person for the job at this critical juncture," Trump said. "He will continue our program of restoring America's standing in the world, strengthening our alliances, confronting our adversaries, and seeking the denuclearization of the Korean Peninsula."

He also urged Pompeo's "swift confirmation", saying his experience in the military, Congress and as leader of the CIA has "prepared him well for his new role."

Trump added that the nomination of Haspel to replace Pompeo was "a historic milestone."

Thanking Tillerson for his services, Trump noted that "a great deal has been accomplished" over Tillerson's 14-month term.

"I wish him and his family well," he said.

Pompeo said in a statement that he is "deeply grateful" for the nomination.

"If confirmed, I look forward to guiding the world's finest diplomatic corps in formulating and executing the President's foreign policy," he said, vowing to work to ensure that "our nation will forever be safe and strong and proud and mighty and free."

The abrupt replacement came as Tillerson had just wrapped up his visit to Africa.

It also came on the heels of Trump's ground-breaking statement last week that he had accepted the invitation of Kim Jong-un, leader of the Democratic People's Republic of Korea (DPRK), for a meeting.

Pompeo's nomination has yet to be approved by the US Congress although it highly unlikely to be vetoed.

Tillerson, former chief executive of the US oil and gas company Exxon, assumed office on Feb 1, 2017. He underwent a rocky term as a newcomer diplomat due to his divergence from Trump on issues like multilateralism and America's withdrawal from multilateral treaties and organizations.

Haspel, a veteran intelligence officer, joined the CIA in 1985 and has served multiple overseas posts in her career. She was reportedly known to pursue harsh interrogation measures, including waterboarding, against alleged terrorists.

When asked by CBS News whether Haspel would sanction more "black sites" after taking the reins, a CIA spokesperson said "this appointment is simply about putting in place the best person for the job."