U.S. House Speaker John Boehner abruptly broke off talks with President Barack Obama Friday night on a deal to make major cuts in federal spending and avert a threatened government default, sending already uncertain compromise efforts into instant crisis.

Within minutes, Obama called on political leaders from both parties to come to the White House Saturday morning for fresh negotiations on raising the nation's debt limit.

"We've got to get it done. It is not an option not to do it," he declared.

For the first time since talks began, he declined to offer assurances, when asked, that default would be avoided. Moments later, however, he said he was confident of that outcome.

At a rebuttal news conference of his own a short while later in the Capitol, Boehner said, "I want to be entirely clear, no one wants default on the full faith and credit of the United States government, and I'm convinced that we will not."

The two men offered sharply different accounts of the compromise efforts so far and who was at fault for the collapse.

"I've been left at the altar now a couple of times," Obama said wryly.

"It's the president who walked away from his agreement," Boehner contended. The Speaker said Obama wanted higher taxes and not enough spending cuts.

The president countered that he had offered an "extraordinarily fair deal" that totalled $2.6 trillion US in spending cuts and $1.2 trillion in additional revenue.

Barring action by Congress by an Aug 2 deadline, the Treasury will be unable to pay all its bills. Officials say a default could destabilize the already weakened U.S. economy and send major ripple effects across the globe.

'Different visions for our country'

In a letter circulated earlier to the House Republican rank and file, Boehner said he had withdrawn from the talks because the president wanted to raise taxes and was reluctant to agree to cuts in benefit programs.

The disconnect was "not because of different personalities but because of different visions for our country," he said, and he announced he would now seek agreement with the Democratic-controlled Senate.

Obama was having none of that, announcing instead a morning White House meeting where he said he expected to hear proposed solutions from the top leaders of both parties in both houses.

"One of the questions the Republican Party is going to have to ask itself is, 'Can they say yes to anything?"' Obama said.

The president avoided direct criticism of Boehner, although he did mention that his phone calls to the Speaker had gone unreturned during the day. One administration official said the president had tried to reach Boehner four times. Asked about the spurned calls, Boehner said he didn't think his relationship with Obama had been "irreparably damaged."

U.S. House Speaker John Boehner said he would attend a debt-limit meeting Saturday at the White House. ((Yuri Gripas/Reuters))

He said he would attend the Saturday meeting at the White House.

Private, sometimes-secret negotiations had veered uncertainly for weeks, generating reports as late as Thursday that the two sides were possibly closing in on an agreement to cut $3 trillion in spending and add as much as $1 trillion in possible revenue while increasing the government's borrowing authority of $2.4 trillion.

That triggered a revolt among Democrats who expressed fears the president was giving away too much in terms of cuts to Medicare and Social Security while getting too little by way of additional revenues.

"Failing to raise the debt ceiling would do irreparable harm to our credit standing, would undermine our ability to lead on global economic issues and would damage our economy," former treasury secretary Henry Paulson, a Republican, told reporters during the day.

Current administration officials and Federal Reserve Chairman Ben Bernanke have said much the same thing for weeks — while gridlock persisted in Congress.

Obama said his only requirement for an agreement was legislation that provides the Treasury enough borrowing authority to tide the government over through the 2012 election.

Senate majority leader Harry Reid, a Democrat from Nevada, agreed in a written statement, saying a shorter-term extension was unacceptable.

His counterpart, Senate Republican leader Mitch McConnell, supported Boehner for "insisting on reducing spending and opposing the president's call for higher taxes on American families and job creators."

Not for the first time, he said, "it's time now for the debate to move out of a room in the White House and onto the House and Senate floors."

The two Senate leaders will be among the legislators at the White House meeting called by the president, presumably joined by Boehner and Representative Nancy Pelosi, the House Democratic leader.

At the same time Obama and Boehner sought to define the clash to their political advantage, their aides provided details of the abortive talks.

Republican aides said the White House had raised their demands for tax increases during the week, in the wake of a proposal by the bipartisan "Gang of Six" in the Senate, who called for an overhaul of the tax code that would increase revenue by $1 trillion over a decade.

Additionally, the aides said the two sides were not able to bridge their differences over the triggers designed to force Congress to enact both tax reform and cuts to Medicare and other benefit programs by early next year.