US President Joe Biden on Monday called on Congress to intervene urgently to prevent a strike by railroad workers that he warned would "devastate our economy."

Biden asked Congress to deploy rarely used legislative powers to force the adoption of a preliminary deal which freight rail companies and workers had announced in September before some of the trade unions backed off, returning to their threat to go on strike.

The Democratic party leader said there was no alternative to forcing through the contested deal, which covers wage increases and working conditions.

"Let me be clear: a rail shutdown would devastate our economy. Without freight rail, many US industries would shut down. My economic advisors report that as many as 765,000 Americans -- many union workers themselves -- could be put out of work in the first two weeks alone," Biden pointed out in a statement.

According to the American Association of Railroads, if an agreement is not reached by December 9, the world's largest economy could see nearly 7,000 freight trains grind to a halt, at a cost of more than $2 billion a day.

Biden said a strike would mean that "communities could lose access to chemicals necessary to ensure clean drinking water. Farms and ranches across the country could be unable to feed their livestock."

A dispute between workers and freight companies has been simmering for months. A strike was narrowly avoided in September after Biden and his top aides intervened in marathon negotiations.

However, four of the 12 unions involved later failed to ratify the deal, sparking the new crisis.

"As a proud pro-labor president, I am reluctant to override the ratification procedures and the views of those who voted against the agreement," Biden claimed.

"But in this case -- where the economic impact of a shutdown would hurt millions of other working people and families -- I believe Congress must use its powers to adopt this deal," he added.

The US President said now was not the time to try and fix an issue plaguing workplaces across the economy.

"I share workers' concern," he said, "but at this critical moment for our economy, in the holiday season, we cannot let our strongly held conviction for better outcomes for workers deny workers the benefits of the bargain they reached, and hurl this nation into a devastating rail freight shutdown."

Biden urged Congress to pass the legislation "well in advance of December 9th so we can avoid disruption."

Nancy Pelosi, the Democratic speaker of the House until January when Republicans take over, said the bill would be put to a vote this week "to prevent a catastrophic nationwide rail strike, which would grind our economy to a halt."

It will then go to the Senate, where the Democrats hold a narrow majority.

Read more: US rail workers' strike could cost $1 Bln in first week: CNN