El Salvador's President Nayib Bukele on Monday said he would not return a man who the Trump administration admits was mistakenly deported to the Central American country as part of a controversial US migration crackdown.

"How can I return him to the United States? It's like, I smuggle him into the United States?... I don't have the power to return him to the United States," Bukele said at a meeting in the Oval Office with President Donald Trump.

The Trump administration has been ordered by a court to facilitate the man's return after he was deported without due process.