By Steve Holland and Andrea Shalal
WASHINGTON, Oct 19 (Reuters) - U.S. President Joe Biden's much-vaunted decades of congressional experience face a serious test in days ahead, as he tries to corral warring Democratic factions on massive spending and infrastructure bills.
U.S. House of Representatives Speaker Nancy Pelosi has set Oct. 31 as the deadline for the House to pass a $1.2 trillion infrastructure deal that has already passed the Senate and has broad bipartisan support, but that deadline is looking increasingly unrealistic, according to sources briefed on negotiations inside and outside the White House.
Biden was to meet separately on Tuesday afternoon with a group of progressive lawmakers who are adamantly insisting that Biden agree to a $3.5 trillion budget bill, and a more moderate group concerned about that level of spending and how to pay for it.
The progressive list includes Representative Pramilia Jayapal, a major mouthpiece of her group, but leaves out liberal firebrand Representative Alexandria Ocasio-Cortez.
The moderate list has Senator Mark Warner but does not include two other Democrats who have steadfastly refused to go along with a $3.5 trillion bill: Senators Joe Manchin of West Virginia and Krysten Sinema of Arizona.
Sinema was spotted at the White House on Tuesday morning ahead of the meetings.
One of Biden's major selling points in last year's presidential campaign was his ability to find a middle ground at a time of deep political polarization, touting his 36 years as a moderate Democratic U.S. senator from Delaware.
Weeks of negotiations, which White House officials say have been productive, have nonetheless failed to bridge the gap on a $3.5 trillion spending bill that advances Biden's campaign pledges on climate, inequality and infrastructure.
Biden said on Oct. 1 that he would find an agreement "whether it's in six minutes, six days or in six weeks" but White House officials are increasingly concerned as the weeks tick by.
Administration officials have steadfastly refused to provide details on specific components of the package - and potential tradeoffs - arguing that they do not want to negotiate in public. They point to concerted efforts by Biden, Treasury Secretary Janet Yellen and others to hammer out a solution in line with their commitment to combat climate change and restructure the U.S. economy to address longstanding inequities.
White House spokeswoman Jen Psaki told reporters on Monday that Biden "is certainly feeling an urgency to move things forward, to get things done."
Biden and White House officials have cautioned progressives that no compromise is to be found on a $3.5 trillion bill and that they need to lower their expectations. The Democrats' left wing is insisting on the full amount, arguing that is what is necessary to deliver what Biden promised voters.
Progressives refuse to go along with the infrastructure deal without an agreement on the other spending bill. Warner has called for an agreement in time to help give a boost to Democrat Terry McAuliffe's Nov. 2 bid for a second term as governor of Virginia.
CLIMATE PLAN UNRESOLVED
It is looking increasingly likely Biden could be forced to go to a climate summit in Glasgow in early November without a key piece of the legislation confirmed - billions of dollars in spending he wants for his climate agenda.
The lack of concrete U.S. legislative changes on climate could thwart Biden's drive to convince the world that "America is back" and an international player again after Republican Donald Trump's four years of divisive global politics.
A senior administration official pushed back against the notion that failure to reach an agreement before the G20 leaders summit in Rome and the global talks on climate in late October and early November would undermine Biden's credibility. "We're in the middle of this process. It's ongoing. People can see that," said the official.
Manchin, the West Virginia senator, said on Tuesday he is not talking about a carbon tax in negotiations over the spending and infrastructure bills, even as some of his fellow Democrats in the Senate support it as a way to fight climate change.
(Reporting By Steve Holland and Andrea Shalal; Editing by Heather Timmons and Alistair Bell)