President Donald Trump has said he has been "totally misrepresented" over accusations he used the term "shithole" to describe African nations last week.
Donald Trump Photo: AFP
Mr Trump also said the allegation was hurting efforts to strike a deal to protect so-called Dreamer immigrants.
The president was responding to a claim by Democratic Senator Dick Durbin that he used "vile and racist" language during a meeting on immigration reform.
The alleged remarks sparked global outrage and demands that he apologise.
"There is no other word one can use but racist," said a UN spokesman.
On Monday, two senators who said he did indeed use the disparaging remark stood by their account of what took place.
The row broke out after Republican and Democratic lawmakers visited the president in the Oval Office on Thursday to work on a proposal for an immigration deal.
A key issue they need to agree on is what to do with an Obama-era scheme that protects some 800,000 young people who entered the US illegally as children - known as the Dreamers.
But the alleged slur was uttered during another topic for discussion - the Temporary Protected Status (TPS) given to a number of nationalities currently living in the country.
In recent weeks the Trump administration has made a series of announcements that have brought that status to an end.
Hours after the meeting, reports emerged that Mr Trump had asked: "Why are we having all these people from shithole countries come here?"
The US should be taking in migrants from countries like Norway, he is reported to have said.
Accounts suggest that when Mr Trump was told that the largest groups of immigrants with that status were from El Salvador, Honduras and Haiti, the president responded: "Haitians? Do we need more Haitians?"
'Hate-filled, vile, and racist'
On Friday, Mr Durbin said: "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.
"President Trump said things that were hate-filled, vile, and racist. He used those words repeatedly."
Mr Trump responded by saying his language was "tough" but not the language used in the news reports. He also denied he was a racist.
And on Monday he tweeted that Mr Durbin had "totally misrepresented what was said".
He also blamed the Democratic senator for the apparent impasse over negotiations to reach a solution on the Dreamers.
Some of the senators present at the meeting have backed him up. Republican David Perdue said the reported racial slur was a "gross misrepresentation", while Republican Tom Cotton "didn't hear Trump use derogatory language".
As well as Mr Durbin's account of events, Republican Lindsey Graham told another senator the reports were "basically accurate".
Three other people who were in the room have remained silent.
The two sides in the row became more entrenched on Monday, with Mr Graham appearing to challenge colleagues Perdue and Cotton by saying his memory had not "evolved".
"I know what was said," he said.
And Mr Durbin also said he stood "behind every word".
He added he was focused "full-time" on finding a "future in America" for "those who are being protected by Daca [Deferred Action for Childhood Arrivals]".
- BBC