The White House is drawing up detailed plans to shut down the federal government from Saturday that would suspend an estimated 800,000 employees and disrupt hundreds of services ranging from processing of tax returns to the closure of national parks, senior Obama administration officials said.

The shutdown will begin at midnight on Friday unless the Democrats and Republicans compromise over this year's budget, part of an ideological battle being waged over the size of the federal government and the soaring national debt.

"We would anticipate significantly lower staffing levels at the White House and across all federal agencies," one of the administration officials, who insisted on anonymity, told reporters.

A shutdown would prompt widespread disruption, hitting health services, courts, housing loans, museums, weather forecasts and other federal government services. Visitors to the US would face delays as embassies stop processing visa applications.

One of the officials said an estimated 800,000 out of the 2.8 million federal employees face being placed on extended leave, during which time they are unlikely to be paid. Exemptions will be made for services viewed as essential for security or safety, such as the military, law enforcement officers, customs officers and other border officials, and homeland security. The military would be paid up until Friday but, though continuing to earn beyond that date, would not receive any further pay cheques until the crisis is resolved.

Democratic senator Chuck Schumer said yesterday there was "a glimmer of hope" that a deal could be reached, his cautious optimism contrasting with a meeting between Barack Obama and the Republican Speaker, John Boehner, at the White House on Tuesday which broke up without agreement and was followed by acrimonious public comments.

The two spoke again yesterday and aides reported the mood was better, though the phonecall lasted for only for three minutes and significant differences remain over where cuts would be made.

Boehner's office said the Speaker told the president he "remains hopeful a deal can be reached and that talks would continue". The statement said: "The Speaker reiterated that the House's goal is to prevent a government shutdown and make real cuts in spending."

Congressional aides worked late on Tuesday and again yesterday on a compromise and reported some progress.

The Obama administration's decision to brief journalists on the details of a shutdown may be an attempt to pressure Republicans.

The first visible sign of the shutdown would be closure signs, already being prepared, going up at Washington's Smithsonian museums and galleries from Saturday, and scores of national parks such as Yellowstone and Yosemite shutting their gates, as will the National Zoo. Events such as the annual Cherry Blossom parade, scheduled for Washington on Saturday, will also be cancelled, an Obama official said.

On a bigger scale, loans for small businesses would not be processed and there would be no home loan guarantees. The tax office would suspend the processing of about 30% of tax refunds. The National Institutes of Health would stop taking new patients.

The official said that those on welfare would continue to receive their cheques, at least for a few months.

Congress would continue, but with many staff seen as non-essential told to stay at home. The courts would be expected to continue functioning as normal, at least for a few weeks.

Jeff Zients, deputy director of the White House's office of management and budget, emailed the heads of federal agencies earlier this week saying it was only sensible that contingency plans were being laid.

"Given the realities of the calendar, good management requires that we continue contingency planning for an orderly shutdown," he said.

The standoff in Washington focuses on the annual federal budget up until this September. Boehner and his Republicans had sought $33bn (£20bn) in cuts and Obama agreed, but Boehner wants a further $7bn in cuts and is demanding that politically divisive areas such as abortion programmes be included.

The Democratic leader in the Senate, Harry Reid, speaking in the chamber yesterday, expressed frustration with Republicans. "Every time we agreed to meet in the middle, they move where the middle is," he said.

The negotiations may turn out to be Republican brinkmanship. The last shutdown, which lasted for six days in November 1995 and a further three weeks from December 1995 to January 1996, cost $1.4bn and backfired on the Republicans, setting up the then President Bill Clinton for re-election in November 1996.

Although the Republicans are under pressure from members of the Tea Party movement who backed them in November's Congressional elections on promises to cut the federal deficit, they are conscious of what happened in 1996 and of current polls. A CNN poll on Monday showed 46% of those surveyed backed Obama's approach to the budget negotiations and 45% the Republican approach.

Much of the Tea Party anger is over the size of the federal deficit, which stands at $14tn, compared with about $5tn at the time of the last shutdown.

Current differences between Democrats and Republicans are relatively small given the overall size of the US budget, making a deal possible. Boehner may emerge to tell supporters he had pushed Obama to the limit and secured more than the White House was prepared to agree to initially.

But bigger budget battles lie ahead, with the Republicans saying this week they are seeking trillions to be cut from the federal deficit in the decade ahead.