WASHINGTON — With the fate of hundreds of thousands of young immigrants hanging in the balance, relations between key Republican and Democratic lawmakers turned poisonous Sunday over disagreement about President Trump’s use of a vulgarity to describe poor countries last week during an Oval Office meeting.

Sens. Tom Cotton, R-Ark., and David Perdue, R-Ga. – who attended the meeting and previously said they could not recall whether Trump had referred to “shithole countries” – on Sunday denied outright that Trump had ever said it. They suggested that a Democrat who publicly confirmed the remarks, Senate Minority Whip Dick Durbin, could not be trusted.

“This is a gross misrepresentation, it’s not the first time Senator Durbin has done it, and it is not productive to solving the problem we’re having,” Perdue said on ABC’s “This Week With George Stephanopoulos.”

The accusations prompted Democrats to blast the Republican senators for impugning a colleague’s integrity, while also slamming Trump and his remarks as unabashedly racist.

The only administration official to speak publicly over the weekend about the meeting was Homeland Security Secretary Kirstjen Nielsen, who attended the session. She said in an interview with “Fox News Sunday” that she did not “recall him using that exact phrase” but acknowledged Trump “did use and will continue to use strong language.”

The president, away for a golf weekend at Mar-a-Lago, made no public appearances.

The White House did not dispute the remarks when The Washington Post first reported them Thursday. Trump offered a vague denial in a Friday tweet, and not until Cotton and Perdue spoke Sunday did another participant challenge whether Trump had used the word “shithole.”

International reaction to Trump’s comments was strong, and U.S. diplomats in Haiti and other nations have been called to host government offices to hear the complaints directly.

“One of the great things about being president is that you can say whatever you want,” State Department Undersecretary Steven Goldstein said in an interview. “We have advised our ambassadors . . . to indicate that our commitment to those countries remains strong.”

The developments together stand to undermine bipartisan talks aimed at shielding from deportation many immigrants brought illegally to the United States as children, including the roughly 800,000 who secured work permits under the Deferred Action for Childhood Arrivals program created under then-President Barack Obama. Democrats have suggested they could force a government shutdown Saturday unless an agreement protecting those “dreamers” is reached.

Conservative hard-liners who want tighter immigration policies and the pro-immigrant and business groups opposing them have long mistrusted one another, but the sniping in recent days has been unusually fierce.

“Both sides now are destroying the setting in which anything meaningful can happen,” said Sen. Rand Paul, R-Ky., a conservative, on NBC’s “Meet the Press.”

A tentative deal worked out Thursday by a small bipartisan group of senators crumbled in an Oval Office meeting in which, according to multiple people involved, an angry Trump asked them why the United States should accept immigrants from “shithole countries” such as Haiti, El Salvador and African nations over those from European countries such as Norway.

In a Sunday morning tweet, Trump declared the immigration talks to be failing: “DACA is probably dead because the Democrats don’t really want it, they just want to talk and take desperately needed money away from our military.”

Democrats have tied the immigration talks to spending negotiations being held ahead of a shutdown deadline at midnight Friday. Republicans are seeking a military spending increase; Democrats want a DACA deal and a matching increase in nondefense funding.

Durbin, of Illinois, the sole Democrat to attend the meeting, told reporters Friday that Trump had used the vulgar word “not just once but repeatedly.” A Republican attendee, Sen. Lindsey Graham of South Carolina, issued a statement that did not specifically confirm the words used but backed up Durbin’s account.

Cotton and Perdue issued a joint statement Friday saying that they did “not recall the president saying these comments specifically.” But Perdue told Stephanopoulos definitively on Sunday that Trump did not refer to “shithole” countries: “I’m telling you he did not use that word, George.”

Cotton said much the same in an interview with CBS’s “Face the Nation”: “I didn’t hear it, and I was sitting no further away from Donald Trump than Dick Durbin was.”

Both senators pointed to a Durbin statement in 2013 about comments allegedly made by an unnamed Republican leader during a private White House meeting that were later denied by an Obama administration spokesman. “Senator Durbin has a history of misrepresenting what happens in White House meetings,” Cotton said.

Ben Marter, a Durbin spokesman, tweeted a rebuke early Sunday: “Credibility is something that’s built by being consistently honest over time,” he said. “Senator Durbin has it. Senator Perdue does not. Ask anyone who’s dealt with both.”

Senate Minority Leader Chuck Schumer, D-N.Y., forcefully backed Durbin, who has written a bill to grant young illegal immigrants a citizenship path and is the leading Democratic negotiator on the DACA issue.

“To impugn (Durbin’s) integrity is disgraceful,” Schumer said on Twitter.

Accounts of the meeting have not fallen neatly along party lines. Besides Graham’s endorsement of Durbin’s account, Sen. Jeff Flake, R-Ariz., said Sunday on “This Week” that he had spoken to meeting participants immediately afterward – before The Post reported Trump’s use of the vulgar term.

“They said those words were used before those words went public,” Flake said.

Nielsen is scheduled to testify under oath Tuesday at Senate Judiciary Committee oversight hearing. Both Durbin and Graham sit on the panel and could press her for details of the Oval Office session.

The “shithole countries” remark has vexed Republicans, compelling many to make statements critical of Trump. “I can’t defend the indefensible,” Rep. Mia Love, R-Utah, whose parents are Haitian immigrants, said Sunday on CNN’s “State of the Union.”

But Democrats see the comment as evidence of malicious intent in Trump’s policymaking.

“I think he is a racist,” Rep. John Lewis, D-Ga., said on “This Week.” “We have to stand out; we have to speak up and not try to sweep it under the rug.”

But Paul called the racism accusations “unfair” and said the “bonkers” outcry over Trump’s remarks could scuttle a deal.

“I do want to see an immigration compromise, and you can’t have an immigration compromise if everybody out there is calling the president a racist,” Paul said.While Democrats have expressed openness to a deal that would combine legal status for dreamers with funding for border security measures, Republicans have tried to broaden the talks. They have targeted the abolition of a special program allowing citizens of some countries to apply for visas distributed by lottery, as well as rules allowing naturalized U.S. citizens to sponsor family members for legal status – a system that Republican critics refer to as “chain migration.”

The tentative deal unveiled Thursday would give legal status and a pathway to citizenship for dreamers while also providing $2.7 billion for border security – some of which could be used to construct the border wall that Trump has proposed. The visas now offered under the lottery system would be reallocated to other immigration programs, such as one offering temporary status to citizens of nations in crisis – such as the ones Trump referenced in his Oval Office remarks.

Trump said in a second tweet Sunday that he wanted more aggressive measures in any deal: “I, as President, want people coming into our Country who are going to help us become strong and great again, people coming in through a system based on MERIT. No more Lotteries!”

Echoing dozens of Democrats, Lewis said he would not vote for any government spending measure until the dreamer issue is settled. “We must not give up or give in,” he said.

Republicans cannot pass a government funding bill without Democratic votes. There are 51 Senate Republicans in a chamber in which 60 votes are needed to pass major legislation, and Republican leaders are facing problems in the House, as well, where some Republican members have balked at the prospect of passing another stopgap that does not increase military funding.

Last week, a federal judge in California halted Trump’s decision to end the DACA program and ruled that program participants should retain their legal status. U.S. Citizenship and Immigration Services said late Saturday that it would resume accepting renewal requests from people already enrolled in the program.

But there is little indication the ruling has defused the standoff. Multiple Democratic aides involved in the effort to secure a compromise said this weekend that the urgency of the situation had not changed and that Democrats are trained on securing a legislative solution to the crisis ahead of the midnight Friday deadline.

Speaking on “Face the Nation,” Sen. Joe Manchin, D-W.Va., urged lawmakers not to let the tussle over Trump’s remarks derail the talks.

“It was hurtful, it’s harmful, it shouldn’t have been said,” he said. “But let’s move on – don’t let it stop the whole procedure.”