Countdown to closure:

Officials began warning Wednesday of significant cutbacks in government services as the threat of a federal government shutdown lurched one day closer to reality.

Failure to reach a budget deal would mean furloughing about 800,000 federal employees nationwide — many of whom are expected to surrender their Blackberrys, according to senior administration officials familiar with shutdown planning. A shutdown might also require organizers to cancel Washington’s storied Cherry Blossom Parade, which is scheduled to occur Saturday morning along the Mall.

The District could feel the impact most especially, with trash collection suspended and D.C. libraries and Department of Motor Vehicle offices closed during a funding lapse unless Congress acts to provide the federal funding needed for those operations, according to the senior officials. Trash collection would not start again until one week after the shut down, and street sweeping would be suspended.

D.C. Mayor Vincent Gray was scheduled to provide an update on the District’s contingency plans at a 2 p.m. news conference.

Congressional staffers from both sides of the aisle continued last-ditch negotiations Wednesday, but showed no sign of bridging their differences over how many billions of dollars to slash from the 2011 budget.

With little more than 48 hours remaining before the current funding resolution expires, federal agency heads, workers, and untold numbers of tourists and Washington-area residents were forced to focus on what life would be like if the government halts non-essential services.

National parks and Smithsonian museums would close. Many government Web sites would stop updating information and many White House staffers would be sent home. Current Medicare, Medicaid and Social Security beneficiaries would continue receiving payments. Taxpayers submitting income tax returns through the mail would not immediately receive payments and federal small business loans would stop.

(RELATED: What will be open? What can I expect?)

Despite the ongoing talks, a senior government official said Wednesday that “From a good housekeeping perspective” the government must begin preparations.

A key question still looming for hundreds of thousands of Washington-area federal workers is whether they would have to work through an impasse — without pay. Departments began answering questions Wednesday morning.

In an e-mail, Health and Human Services Secretary Kathleen Sebelius said she and the president “are very much aware that a shutdown would impose hardships on many employees as well as the groups and individuals our department serves.”

But “prudent management requires that I plan for an orderly shutdown should Congress fail to pass a funding bill.” If a shutdown occurs, Sebelius said workers will learn their fates no later than Friday.

Federal employees received similar messages across the government with a link to a Q&A answering several queries regarding pay and benefits. The Q&A did not answer simple logical questions regarding a shutdown — including who would collect Blackberrys and when they would be returned; officials familiar with shutdown planning said those details are forthcoming.

Rep. James Moran (D-Va), whose Northern Virginia district is home to thousands of federal employees, said furloughed workers should not expect to be paid, based on feedback he is getting from Republican colleagues in Congress.

“It is highly unlikely that about 1 million federal employees who are not working will ever be reimbursed,” Moran said in a conference call Wednesday with reporters. He called the majority of his GOP colleagues “far more anti-government in terms of their mindset” than former House Speaker Newt Gingrich during the 1990s shutdown, when Congress agreed to reimburse furloughed workers retroactively.

Despite the threat of cancellation, Cherry Blossom parade spokeswoman Danielle Piacente said organizers are discussing alternate plans. “We’re optimistic that the festival parade and other festival events will move forward as scheduled,” she said, urging potential attendees to visit the parade Web site for updates.

Other blossom events, in addition to the parade, wouldn’t be affected by a shutdown, Piacente said, including the Sakura Matsuri Japanese street festival.

If canceled, she said it is unclear whether the parade would be rescheduled this year. The festival brings $100 million a year into the region from blossom visitors.

“We have marching bands coming from Ohio,” Piacente said in an interview. “We have marching bands coming from Wisconsin. We have lots of people coming into town for this parade.”

“We’re just taking it day by day,” she said. “We’re basically reaching out to everyone that we possibly can to figure out how to make the parade happen...We’re optimistic.”

National Park Service spokesman Bill Line said he was not certain how a shutdown would affect monuments and memorials on the Mall. Would memorials be closed? If so, how? “We’re in a hypothetical clouds of could bes,” he said. He noted that park ranger cherry blossom walks and bike tours would likely not take place, although he said they only happen on weekends, and the cherry blossom festival ends Sunday.

Senior administration officials Wednesday could not quantify the potential national economic impact of a shutdown, but rattled off several ways the economy could be impacted: The Environmental Protection Agency would cease environmental impact assessments, potentially derailing large-scale construction projects. The Small Business Administration would stop doling out loans to small businesses, disrupting the ongoing economic recovery. The Federal Housing Administration would be unable to provide guarantees on new home loans, forcing first-time home buyers to postpone closing dates.

Smaller agencies would also shutter almost completely. At the Government Accountability Office, the federal watchdog agency, only the general counsel, chairman and some security officers would be allowed to work.

Since federal courts are deemed an essential government function under U.S. law, trials will continue and people can file lawsuits even during a government shutdown. "Judicial functions will continue,'' said David Sellers, spokesman for the Administrative Office of the U.S. Courts.

If a shutdown lasts longer than two weeks, certain court functions would be affected, but it is unlikely the public would see any impact, Sellers said. Payments would be delayed for jurors and for lawyers appointed to represent indigent defendants. "You won't have any contracts moving ahead, new equipment, advances in technology,'' Sellers said. "The behind-the-scenes things that support the courts.''

For the first two weeks of any shutdown, Sellers said, the courts would avoid even those effects by using reserve funds.

Despite the widespread, high-profile closures, several fee-based government operations, or agencies funded through multi-year budgets would stay open, including the Veterans Health Administration, elements of the U.S. Patent and Trademark Office and the Federal Highway Administration, which uses money from the federal highway trust fund.

Whether all of this can be avoided rests with lawmakers and White House officials who plan to continue talking all day Wednesday.

Staff writers Lisa Rein, Karen Tumulty, Jerry Markon and Brian Vastag contributed to this report.

RELATED: The Federal Eye’s government shutdown coverage