By David Morgan and Richard Cowan
WASHINGTON (Reuters) - The U.S. Senate could pass a $2 trillion coronavirus economic stimulus package as soon as Tuesday, negotiators said, insisting they had made significant progress despite failing so far to reach a bipartisan deal on the sweeping legislation.
Steven Mnuchin, President Donald Trump's treasury secretary, said he would return to the Capitol for more talks on Tuesday, after a day of negotiations ended at midnight without an agreement. The Senate is due to convene at 10:00 a.m. ET (1400 GMT).
Neither Mnuchin nor Senate Democratic Leader Chuck Schumer would provide details, but both were optimistic.
"That's the expectation, that we will finish it tomorrow and hopefully vote on it tomorrow," Schumer told reporters.
Republicans, Democrats and top Trump aides had negotiated for days over the package, which would be the third and largest passed to address the crisis if it is backed by both the Republican-majority Senate and Democratic-majority House of Representatives.
Republicans have objected that Democrats are trying to add unrelated provisions, such as support for renewable energy.
"Congress must approve the deal, without all of the nonsense, today. The longer it takes, the harder it will be to start up our economy," Trump wrote on Twitter on Tuesday.
To become law, the measure must be signed by Trump. Mnuchin said he had spoken with the president at least 10 times during the marathon negotiating session on Monday.
Democrats have twice blocked attempts to advance the bill, saying it did not provide enough money for states and hospitals, lacked sufficient aid for unemployed Americans and did not include adequate supervision of a massive fund to aid big businesses.
Those concerns appear to have been addressed.
"I'm very optimistic that there will be a deal announced this morning," Democratic Senator Chris Coons said on MSNBC.
The coronavirus pandemic has killed more than 550 people in the United States and sickened more than 43,800, shuttered thousands of businesses, thrown millions out of work and led state governors to order about 100 million people - nearly a third of the nation's population - to stay at home.
Democratic House Speaker Nancy Pelosi, who was consulted in the talks, has introduced her own $2.5 trillion counterproposal that also includes $4 billion that would allow states to conduct the November presidential and congressional elections by mail.
That legislation would likely be irrelevant if a bipartisan deal is forged in the Senate.
It was not clear early on Tuesday whether Pelosi supported the latest developments.
Trump's administration has launched a major push for action to blunt the economic impact of the pandemic and steep stock market decline, after Trump spent weeks dismissing the risks.
While details of the emerging bipartisan bill were not available, it is expected to provide financial aid for Americans out of work because of the virus and help for struggling industries such as airlines.
Republicans normally hold a slim 53-47 majority in the Senate, meaning they need Democratic support to garner the 60 votes required to advance most legislation.
But the coronavirus has trimmed their ranks, giving Democrats even more leverage. Republican Senator Rand Paul has tested positive for coronavirus and four other Republicans are also unable to vote because they were exposed to Paul or others with the virus.
(Additional reporting by Patricia Zengerle and Susan Cornwell; Writing by Patricia Zengerle and Andy Sullivan; editing by Gerry Doyle, Bernadette Baum and David Gregorio)