(Bloomberg) -- President Joe Biden is attempting to mediate between Democratic moderates and progressives, as squabbling between the two wings of the party threatens to sink his economic agenda.

Biden’s Oval Office overture comes in tandem with stepped-up efforts by the administration to reach out to lawmakers, either in groups or in individual meetings as the president tries to assert more control over a package that is still being put together in Congress. 

Biden and Democratic congressional leaders are seeking middle ground on tax and spending legislation encompassing most of Biden’s domestic agenda. The future of that and a separate infrastructure bill depends on party unity.

The president met first with House Speaker Nancy Pelosi and Senate Majority Leader Chuck Schumer before separate discussions with groups representing the rival Democratic factions.

“We’re working hard and we’re moving along,” Schumer said after the meeting, refusing to provide any details of the talks.

Democratic leaders are seeking to lower expectations among House progressives, warning that the initial $3.5 trillion price tag may be cut to get full support from moderates, particularly in the Senate, where Democrats can’t afford to lose a single vote. Senators Joe Manchin of West Virginia and Kyrsten Sinema of Arizona have said they don’t support the size of the package, but haven’t said what level of spending they’d agree to.

Manchin and Sinema are scheduled to be in an afternoon meeting that also includes outspoken House centrists like Josh Gottheimer of New Jersey and Stephanie Murphy of Florida, who have demanded the process be slowed down and that the bill not add to the deficit. They also want the House to give final passage next week to bipartisan infrastructure legislation with $550 billion in new spending, before taking up the larger package. Gottheimer is leading a fight to restore the state and local tax deduction,  for wealthy homeowners. That meeting also will include moderate senators like Jon Tester of Montana and Mark Warner of Virginia. 

“When the president gets involved, that’s when the real negotiations start,” Manchin told reporters ahead of the meeting. 

The second meeting will feature 10 progressives including Representatives Pramila Jayapal of Washington and Mark Pocan of Wisconsin as well as Senators Bernie Sanders of Vermont and Ron Wyden of Oregon.

These lawmakers want to change the draft House bill to increase social welfare benefits and increase taxes on the wealthy while reducing subsidies for fossil fuels. Jayapal and her progressive caucus are threatening to vote down the infrastructure bill Monday if the larger package is not enacted first. The meeting includes less confrontational progressives like Barbara Lee of California and Jim McGovern of Massachusetts. That group also includes Senator Patty Murray of Washington, a former chair of the Budget Committee whose views are more in line with the administration’s. 

House and Senate Democrats still haven’t completed the expansive package that includes a mix of tax increases on the wealthy and corporations, as well as greater spending on child and elder care, health care, climate change and other areas. And Democratic leaders acknowledge plans for votes this month could be delayed. 

The package is taking on added importance as other aspects of Biden’s domestic agenda run into significant setbacks or even insurmountable roadblocks. 

Senate Republicans later this month are expected to block for a third time Democratic legislation overhauling U.S. voting laws that is designed to counter a record number of new voting restrictions emerging from GOP-led state legislatures. And earlier this week, the Senate parliamentarian blocked Democrats from including a plan to provide legal status to as many as 8 million undocumented immigrants in the economic package, which Democrats seek to pass without any GOP support using Senate rules that short-circuit the filibuster.

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