WASHINGTON Republican US House Speaker Kevin McCarthy on Sunday dismissed vehement opposition among party hardliners to a new agreement with President Joe Biden to suspend the US$31.4 trillion debt ceiling, predicting that most House Republicans would support the deal.

After weeks of tough negotiations, McCarthy and Biden reached a tentative agreement this weekend, but now face the challenge of getting a deal through the Republican-controlled House of Representatives and Democratic-led Senate before June 5, to avoid a crippling first-ever default.

The president and House speaker were due to speak on Sunday afternoon to finalise the agreement, which has drawn fire from hardline Republicans and progressive Democrats. House Republicans expected to unveil legislation to pass the deal later on Sunday.

Members of the hardline House Freedom Caucus said they would try to prevent the agreement from passing the House in a vote expected on Wednesday. "We're going to try," Representative Chip Roy, a prominent Freedom Caucus member, said in a Sunday tweet.

But McCarthy dismissed threats of opposition within his own party, saying "over 95%" of House Republicans were "overwhelmingly excited" about the deal.

"This is a good strong Bill that a majority of Republicans will vote for," the California Republican told reporters in the US Capitol. "You're going to have Republicans and Democrats be able to move this to the president."

To win the speaker's gavel, McCarthy agreed to enable any single House member to call for a vote to unseat him, potentially making him vulnerable to ouster by disgruntled Republicans. The speaker said he was "not at all" concerned about that possibility.

Republicans control the House by 222-213, while Democrats control the Senate by 51-49. These narrow margins mean that moderates from both sides will have to support the Bill, if the compromise loses the support of the far left and far right wings of each party.

"I'm not happy with some of the things I'm hearing about," Representative Pramila Jayapal, who chairs the Congressional Progressive Caucus, told CNN's "State of the Union".

House Democratic leader Hakeem Jeffries said he expects Democratic support for the deal on CBS's "Face the Nation", but declined to estimate how many of his party members would vote for it.

Democrats, who were due to be briefed on the deal at 5 p.m.(2100 GMT) by the White House, had feared the agreement would parallel a Republican debt ceiling plan that passed the House last month and would have imposed deep cuts on domestic spending.

Democratic Representative Jim Himes told Fox News that the deal's relatively "small" scope could attract support from members of Biden's party.

The deal suspends the debt ceiling until January 2025, after the November 2024 presidential election, while boosting spending on the military and veterans' care, and capping it for many discretionary domestic programmes, according to sources familiar with the talks.

McCarthy also told Fox News that the deal includes a "paygo" measure that requires the administration to ensure that new spending does not increase the deficit. The deal would also impose a 1% across-the-board spending cut,  should Congress fail to enact 12 appropriations bills by Oct 1.

Roy complained on Twitter on Sunday that the agreement would leave intact an expansion of the tax-collecting Internal Revenue Service set in place when Democrats controlled both chambers of Congress.

Republican Senator Lindsey Graham also expressed concern about the deal's potential effect on US defence and Washington's support for Ukraine.

"Do not intend to default on debt, but will not support a deal that reduces the size of the Navy and prevents continued technological and weapons assistance to Ukraine," Graham tweeted.

"Punting at your opponent's one-yard line isn't a winning strategy," Republican Senator Mike Lee said on Twitter.

Representative Dan Bishop and other hardline Republicans were sharply critical of early deal details that suggest Biden has pushed back successfully on several cost-cutting demands on Saturday, signaling that McCarthy may have an issue getting votes.

"Utter capitulation in progress. By the side holding the cards," Bishop said.

Progressive Democrats in both chambers have said they would not support any deal that has additional work requirements for food and healthcare programmes. This deal does, sources say, adding work requirements to food aid for people aged 50 to 54.

Several credit-rating agencies have put the United States on review for a possible downgrade, which would push up borrowing costs and undercut its standing as the backbone of the global financial system.

  - Reuters