The Republican-controlled U.S. Congress will begin voting on Tuesday on the biggest overhaul of the U.S. tax system in more than 30 years, with little standing in the way of the party's first major legislative triumph under President Donald Trump.

The House of Representatives, which introduced initial tax legislation barely six weeks ago on Nov. 2, was poised to act first with a Tuesday afternoon vote.

The Senate could follow on Tuesday night or Wednesday morning, after completing 10 hours of debate, lawmakers said.

With strict party-line votes expected in both chambers, passage appeared all but certain.

Republicans insist that the sweeping package of tax cuts for corporations, small businesses and individuals will boost economic and job growth. They also see the measure as key to having any hope of retaining their majorities in the House and Senate when voters go to the polls next November.

The end-of-year sprint toward passage represents a remarkable recovery of Republican fortunes since the middle of this year, when the party's drive to dismantle former Democratic President Barack Obama's Obamacare healthcare law crumbled in the Senate and prospects for a tax overhaul seemed doomed by party infighting.

Lingering doubts about fate of the tax bill all but vanished on Monday after two of the last Senate Republican holdouts, Susan Collins and Mike Lee, agreed to support the legislation.

"I'm ready to vote," Republican Senator John Kennedy told Reuters. "I felt like we should have voted this weekend."