The U.S. is expelling South Africa's ambassador, Secretary of State Marco Rubio said, calling the envoy a "race-baiting politician" who hates President Donald Trump.

Ties have slumped since Trump cut U.S. financial aid to South Africa, citing disapproval of its land policy and its genocide case against Washington's ally Israel at the International Court of Justice.

"Ebrahim Rasool is a race-baiting politician who hates America and hates @Potus (Trump)."

In statements from its presidency and international relations department, South Africa called the move regrettable but said it remained committed to building mutually beneficial relations and would address the matter via diplomatic channels.

Rubio reposted an article from right-wing website Breitbart that quoted the envoy as saying that Trump was leading a white supremacist movement. Rasool must depart by March 21, a State Department spokesperson said on Saturday.

News website Semafor reported this week that Rasool has failed to secure routine meetings with State Department officials and key Republican party figures since Trump, a Republican, took office in January.

The U.S. is reviewing its South Africa policy, the State Department spokesperson added, citing the land policy, South Africa's growing ties with countries like Russia and Iran, and "aggressive positions" toward the U.S. and its allies.