WASHINGTON - The House voted Wednesday to force a deal between freight rail carriers and unions, blocking a potential strike that threatened travel, supply chains and the busy holiday shopping season.

The legislation heads to the Senate, where its path could be more fraught, but leaders of both parties have vowed to act quickly.

Without a deal, the unions are poised to strike as early as Dec. 9. Four of 12 unions involved had voted down a contract, brokered by the White House, that lacked paid sick days or changes to an attendance policy that rail workers say is punitive. A shutdown of the nation's railway systems could cost the economy as much as $2 billion a day, according to the rail carriers trade group.

The House voted 290-137, with bipartisan support, on the bill that would force the rail deal that was brokered by the White House. But the chamber also narrowly approved a separate version of the rail deal, 221-207, to give rail workers seven paid sick days, a move that liberal Democrats in the House, as well as Sen. Bernie Sanders (I-Vt.), have pushed for.

"Today we are here to safeguard the financial security of America's families, to protect the American economy as it continues to recover and avert a devastating nationwide rail shutdown," House Speaker Nancy Pelosi (D-Calif.) said at the start of the floor debate.

Both bills head to the Senate, but timing on the votes there is uncertain.

Shortly after the House action, President Joe Biden urged the Senate to act quickly to avert a rail strike.

"Without the certainty of a final vote to avoid a shutdown this week, railroads will begin to halt the movement of critical materials like chemicals to clean our drinking water as soon as this weekend," Biden said in a statement. "Let me say that again: Without action this week, disruptions to our auto supply chains, our ability to move food to tables, and our ability to remove hazardous waste from gasoline refineries will begin."

The bizarre politics around the rail strike - with the economic threat of an infrastructure shutdown prompting a pro-union Democratic president to push an agreement despite some union workers' objections - makes it harder to predict the bill's path in the Senate.

Several liberal senators, including Sanders and Elizabeth Warren (Mass), were pressing to adopt the version of the agreement that included paid sick days, while moderate Sen. Joe Manchin (D-W.Va.) said he was undecided on whether he'd vote to add the sick days. Labor Secretary Marty Walsh and Transportation Secretary Pete Buttigieg are expected to talk with Democrats about the agreement on Thursday.

On the Republican side, at least one senator, Josh Hawley of Missouri said he would only favor an agreement that included sick days. "I will absolutely not support it without some sick leave," he said. Others who previously seemed open to adding the leave, including Sen. John Cornyn of Texas, walked back that support on Wednesday, saying they did not wish to alter an agreement that had already been reached.

"I doubt very much it makes sense for us to try to rewrite the agreement," said Sen. Pat Toomey (R-Penn.) about the addition of sick days.

Sen. Susan Collins (R-Maine), a moderate who can often be relied upon to take politically tough bipartisan votes, urged Biden to "convene both sides" at the White House and work out another deal instead of having Congress impose one. "To overturn the workers' rejection of the proposal, especially when it centers around sick leave, is troubling to me," she said.

But many Republicans sounded wary of allowing a strike to disrupt the nation's economy, even if they were undecided on how they would vote on the deal. "I don't think the country can stand a rail strike," Sen. Mike Braun of Indiana said. "The economy has been so screwed up over the last two years with the supply chain and other issues."

Even among Democrats, there was disagreement on the path forward. A group of 12 liberal senators released a statement saying the Senate must make the deal "better."

Sanders declined to say on Wednesday whether he would vote for the underlying agreement if he is able to take a separate vote on paid leave.

In recent weeks, four rail unions out of 12 voted down the tentative agreement brokered with help from the White House. That deal offers union members a 24 percent raise by 2024, annual bonuses of $1,000 and a cap on health-care premiums. Carriers also agreed to give conductors and engineers a single additional paid day off and new flexibility to take off work three times a year for routine health appointments without fear of discipline.

But many workers argue that these gains do not address issues related to chronic understaffing that prevent them from going to the doctor and dealing with emergencies, as well as the lack of paid sick days.

Rail carriers have said they need to maintain their attendance policies to ensure the railroads are adequately staffed. They say employees can take time off when they are sick by using paid vacation days.

Ian Jeffries, president of the Association of American Railroads, the industry trade group negotiating on behalf of carriers, said he did not support adding paid sick days to the deal.

"The House is considering a new measure to the equation based on the wholly false premise that rail employees do not get paid sick leave," Jeffries said. "The ramifications of approving such a measure would disincentivize future voluntary agreements for freight railroads."

Michael Baldwin, president of the Brotherhood of Railroad Signalmen, one of the four unions whose members voted down the deal, said his union members were disappointed with Biden's call to Congress to impose the deal. But he is optimistic they can get paid sick days into their contract.

"We're very happy with the vote results from the House today on the resolution to" get sick days, Baldwin said. "We're trying to work within the Senate to see if we can get support, and we're actually starting to get support from people."