By Richard Cowan and Susan Cornwell

WASHINGTON, May 15 (Reuters) - The U.S. House of Representatives is set on Friday to debate and vote on a $3 trillion Democratic bill aimed at salving the heavy human and economic toll of the coronavirus pandemic that has caused almost 85,000 U.S. deaths and shut much of the economy.

House Speaker Nancy Pelosi and her fellow Democrats crafted the far-reaching legislation that Senate Republicans have promised will be "dead on arrival" in their chamber.

The House measure includes $500 billion in aid to state governments, another round of direct payments to individuals and families to help stimulate the ailing economy, and hazard pay to healthcare workers and others on the front line of the coronavirus pandemic.

If passed, it would double the amount of spending that Congress has authorized since March to fight the coronavirus.

But unlike the previous four coronavirus-response bills approved by Congress in recent months, this one appears ready to land on the House floor with little to no support from Republicans.

"This week, the speaker published an 1,800-page seasonal catalog of left-wing oddities and called it a coronavirus relief bill," Republican Senate Majority Leader Mitch McConnell groused in a Thursday speech.

McConnell and other Republican leaders in Congress have said more time is needed to gauge the effectiveness of the $3 trillion in aid already enacted into law.

McConnell has added that any new legislation must be aimed at protecting businesses from liability lawsuits as they reopen during the pandemic - at President Donald Trump's urging.

Pelosi responded to McConnell's attack, saying: "He wants us to ‘just pause.’ Well, families know that hunger doesn’t take a pause. Not having a job doesn’t take a pause. Not being able to pay the rent doesn’t take a pause."

Some 36.5 million people in the United States have filed for unemployment since the crisis began, representing more than one in five workers.

Highlighting the crisis' economic fallout, California Governor Gavin Newsom on Thursday proposed deep government spending cuts in response to the coronavirus pandemic that has throttled the economy of the country's most-populous state.

Warning of further reductions without federal aid, the Democratic governor pleaded for help from Congress, saying: "That's the purpose of the federal government - to protect us."

SOCIAL DISTANCING IN HOUSE

Friday's vote, which comes as some moderate and liberal Democrats have expressed doubts about rushing the legislation through, is likely to bring about 400 or so House members back to Washington for only the third time since late March.

It will be governed by strict rules to achieve social distancing and other protective measures so that Congress does not become a breeding ground for the very illness it is trying to battle.

Given Republican opposition, Pelosi's gambit might mainly spark a new round of negotiations among the Republican-controlled Senate, the Democratic-led House and the Republican White House.

McConnell said on Thursday he was open to another coronavirus relief bill and was talking to members of Trump's administration about possible legislation. But he declined to say in an interview with Fox News when his party might start negotiating another such bill.

Representative Tom O'Halleran, a Democrat representing an Arizona district that Trump won in 2016, tweeted that while there were "many merits" to the House bill, called the "Heroes Act," it "won't receive a hearing or markup, and hasn't passed through appropriate committees of jurisdiction."

Besides the coronavirus bill, the House will also try to pass a measure on Friday that would allow members for the first time to cast votes in the chamber by proxy during the pandemic.

Many Republicans are also opposing that measure, saying it was essential that lawmakers vote in person in the House.

Pelosi said she did not know when the House would resume regular sessions, noting that Washington's city government had pushed back its shelter-in-place order to June 8. “I would hope it wouldn’t be any longer than that," Pelosi told reporters. (Reporting by Richard Cowan and Susan Cornwell; Additional reporting by Sharon Bernstein in Sacramento, California, and Lisa Lambert and Mohammad Zargham in Washington; Editing by Scott Malone and Peter Cooney)