US President Donald Trump is preparing to invoke emergency powers as the country struggles to contain the coronavirus outbreak in the United States, according to two people familiar with the planning who spoke on condition of anonymity.

It was still unclear on Friday, however, precisely what mechanism Trump would use to free up additional federal resources for testing and treatment as well as help those struggling with the economic effects.

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Trump is expected to speak at 3pm (19:00 GMT) at the White House. "Topic: CoronaVirus!" he tweeted.

The move comes as House Speaker Nancy Pelosi and the Trump administration are labouring to finish a coronavirus aid package on Friday that would fast-track federal aid to anxious Americans and calm teetering financial markets amid the global crisis.

Central to the effort is free testing for the virus and guaranteed sick pay for workers who are taking time away from jobs, along with an infusion of dollars to handle unemployment benefits and boost food programmes for children, families and seniors.

Pelosi and Treasury Secretary Steven Mnuchin indicated a deal was within reach after days of around-the-clock negotiations, with expectations of a Friday announcement. The House could then swiftly vote. Republican leaders are reviewing the details.

Pelosi exchanges an elbow bump, exhibiting caution amid coronavirus concerns, with Senate Majority Leader Mitch McConnell at a Friends of Ireland luncheon on Capitol Hill [Tom Brenner/Reuters]

Republican leaders in Congress want to be sure that Trump publicly supports the package before they sign off on it ahead of any vote, according to a top congressional aide unauthorised to discuss the private talks and speaking on condition of anonymity.

Earlier on Friday, Mnuchin sounded an optimistic note. "I think we're very close to getting this done," he said in an appearance on CNBC.

On the COVID-19 illness, Mnuchin cautioned that "people should understand the numbers are going to go up before they go down".

Sick pay for workers

Providing sick pay for workers is a crucial element of federal efforts to stop the rapid spread of the infection. Officials warn that the nation's healthcare system could quickly become overwhelmed with gravely sick patients, as it suddenly happened in Italy, one of the countries hardest hit by the virus.

The ability to ensure paycheques will keep flowing - for people who stay home as a preventive measure or because they are feeling ill or caring for others - can help assure Americans they will not fall into financial hardship.

"We're in an emergency, and we're trying to respond as fast as we can," said House Appropriations Committee Chairwoman Nita Lowey, a Democrat, as lawmakers filed in and out of Pelosi's office on Friday.

Late on Thursday, Pelosi said an agreement on an aid package was near. She said a deal was "subject to an exchange of paper and we hope to have an announcement tomorrow". Pelosi and Mnuchin spoke again on early Friday.

A healthcare worker holding a completed test with patient samples at a drive-through testing site for coronavirus, flu and RSV in Seattle, Washington state [Lindsey Wasson/Reuters]

The potential deal between Congress and the White House would cap a tumultuous week in which Washington strained for a comprehensive response to an outbreak that is testing the nation's political, financial and healthcare systems.

Trump has struggled to show he is on top of the crisis, after giving conflicting descriptions of what the US is doing to combat the virus. Classes, sport events, concerts and conferences have been cancelled across the nation, and the financial markets have been cratering.

In one welcome announcement, the administration said on Friday it is awarding $1.3m to two companies trying to develop rapid COVID-19 tests that could detect within an hour whether a person is positive for the new coronavirus.

The House aid package builds on an emergency $8.3bn measure approved last week and is aimed at providing additional health and financial resources to arrest the sudden spread of the pandemic and the kind of economic fallout unseen in a generation. Pelosi promised in a letter to colleagues that a third package was yet to come.

The new sick leave benefit would require businesses to provide up to 14 days of paid leave, with the federal government reimbursing them through tax credits. The bill facilitates unemployment benefits for those laid off during the crisis and boosts food and nutrition programmes for working families, students and seniors. Work requirements for food stamps would be suspended, and states would be given additional Medicaid funds to cope with the crisis.

"We felt that putting together something that the American people can see cooperation on between the two parties in this difficult moment would be a confidence builder," said Democratic Representative Richard Neal, the chairman of the Ways and Means Committee.

Speaker of the House Nancy Pelosi arrives for a briefing by Director of the National Institute of Allergy and Infectious Diseases at the National Institute of Health Dr Anthony Fauci for members of the House on coronavirus on Capitol Hill [Joshua Roberts/Reuters]

Pelosi promised a third coronavirus package will follow soon, though the House is leaving Washington, DC on Friday for a previously scheduled recess. That measure will include more aggressive steps to boost the US economy, which economists fear has already slipped into recession.

But there is little appetite within either party for Trump's proposal to suspend collection of the 6.2 percent Social Security payroll tax, and Democratic economic stimulus ideas like more generous food stamp benefits are not favoured by Republicans, while Democrats are not very friendly to Republican ideas like easing business regulations. States are already clamouring for fiscal relief from Washington as the virus threatens their budgets.

Mnuchin, however, said on Friday the president remains committed to pursuing the payroll tax cut. "It is a giant stimulus."

Disruptions from the virus spread throughout the Washington metropolitan area, as the Capitol, White House and the Supreme Court declared themselves off-limits to the public for now, symbols of a nation hunkering down. And schools in the District of Columbia announced they would close, starting Monday, until April 1.

The storied Smithsonian said it was cancelling all public events and will temporarily close its network of museums and the National Zoo, starting Saturday. And Trump proposed postponing this summer's Olympics in Japan for a year, too.

Trump said he will halt his signature campaign rallies, telling reporters he needs a "little separation until such time as this goes away". Democratic presidential rivals Joe Biden and rival Senator Bernie Sanders said they would no longer hold large political gatherings and their staff would work from home as the race for the presidency moved online.

Politicians hit with virus

The coronavirus crisis also got personal for Trump and some members of Congress.

Australian Home Affairs Minister Peter Dutton was in isolation at a hospital after testing positive for the coronavirus. He returned to Australia on Sunday from Washington, DC, where he met Attorney General William Barr and Trump's daughter, Ivanka, last week.

White House officials, including representatives for Ivanka Trump, have not responded to questions about whether they intend to be tested or self-quarantine.

The White House has insisted officials are following CDC guidelines and that "there is currently no indication to test patients without symptoms, and only people with prolonged close exposure to confirmed positive cases should self-quarantine."

Barr, meanwhile, was staying home on Friday, though he "felt great and wasn't showing any symptoms", according to his spokeswoman Kerri Kupec. She said the CDC did not recommend testing at this point.

Brazil's Communications Secretary Fabio Wajngarten posing with US President Donald Trump [Courtesy: Instagram/Fabio Wajngarten]

In addition, just days after meeting Trump and Republican Senator Rick Scott, the communications chief for Brazil's president, Fabio Wajngarten, tested positive for coronavirus. A photo of the president, the senator and Wajngarten shows the trio shoulder-to-shoulder at Trump's Mar-a-Lago resort last weekend. Scott said he was isolating himself. Trump, 73, said he was unworried.

"We had dinner in Florida at Mar-a-Lago with the entire delegation," Trump told reporters at the White House. "But we did nothing very unusual. We sat next to each other for a period of time." Asked whether he should be tested, Trump replied, "I am not concerned."

White House spokeswoman Stephanie Grisham said the White House is aware of public reports that a member of the Brazilian delegation tested positive. Confirmatory testing is pending.

"Both the President and Vice President had almost no interactions with the individual who tested positive and do not require being tested at this time," Grisham said in a statement. Republican Senator Lindsey Graham, who was also at Trump's club on the weekend, joined a growing list of politicians who have chosen to isolate themselves as a precaution. He announced Friday that he also met the Australian official who has now tested positive.

Republican Senator Ted Cruz, who had previously isolated himself after a potential exposure at a conservative conference in Washington, said on Friday he met a Spanish official and is now self-quarantining.

'Flying blind'

Legislators from both parties expressed alarm at the US response, and especially over how few patients have been tested.

"We're basically, in my opinion, flying blind," said Democratic Representative Susie Lee.

Dr Anthony Fauci, infectious diseases chief at the National Institutes of Health, in several television interviews on Friday, said more tests would be available over the next week, but that officials should not wait before trying to mitigate the virus's effects.

Vehicle Maintenance Utility Service Worker Thiphavanh 'Loui' Thepvongsa wipes down an off-duty bus with a disinfectant during a routine cleaning at the King County Metro Atlantic and Central Base in Seattle, Washington [File: Jason Redmond/Reuters]

"We will have considerably more testing in the future, but you don't wait for testing," Fauci said on "CBS This Morning." He said school closing and similar measures are "generally an appropriate approach".

"We're at a critical point now as we seek to blunt the rise in cases to make sure it's a hill, not a mountain," Fauci said on ABC's Good Morning America.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause severe illnesses, including pneumonia.

The vast majority of people recover. According to the World Health Organization, people with mild illness recover in about two weeks, while those with severer illness may take three to six weeks to be over it. In mainland China, where the virus first exploded, about 81,000 people have been diagnosed and about 64,000 have recovered.