US President Donald Trump has sparked outrage after he was reported to have used crude language to describe foreign countries in an Oval Office meeting.
Trump said he did not say "anything derogatory" about Haitians and appeared to deny calling any countries "shitholes", as was reported, generating a worldwide backlash.
However, Democratic Senator Dick Durbin said Trump used "racist" language.
The president did call some African nations "shitholes", he said.
Amid widespread coverage of his reported remarks at a private meeting with lawmakers to discuss immigration on Thursday, Trump on Friday tweeted his language at the meeting "was tough, but this was not the language used".
Many US media outlets reported the comments on Thursday, quoting witnesses or people briefed on the meeting. The White House did not deny them.
"I cannot believe that in the history of the White House, in that Oval Office, any president has ever spoken the words that I personally heard our president speak yesterday," Durbin told reporters on Friday.
Trump ignored press questions about the issue as he signed a proclamation declaring a holiday in honour of civil rights hero Martin Luther King Jr. - as presidents do every year.
He said Americans were celebrating that "self-evident truth" that "no matter what the colour of our skin or the place of our birth, we are all created equal by God".
Trump's reported remarks came as both Republican and Democratic lawmakers visited him on Thursday to propose a deal on immigration.
Trump was said to have told them that instead of granting temporary residency to citizens of countries hit by natural disasters, war or epidemics, the US should instead be taking in migrants from countries like Norway.
"Why are we having all these people from shithole countries come here?" the Washington Post quoted him as saying, in remarks first reported to be about Haiti, El Salvador and African nations.