WASHINGTON (Reuters) — The U.S. Senate moved slowly on Sunday toward passing a $1 trillion bipartisan infrastructure bill, held back by one Republican lawmaker who opposed speeding up a vote on the nation’s biggest investment in roads and bridges in decades.

The Senate convened at noon EDT and was expected to hold two procedural votes on Sunday evening unless Republicans and Democrats can reach an agreement on amendments to the package resulting from months of bipartisan talks.

The legislation is a top priority for President Joe Biden. Its passage, which remains likely after a large majority has repeatedly voted to advance, would represent a major victory for him and the group of bipartisan lawmakers who crafted it.

The legislation took an important step forward on Saturday, when 67 lawmakers, including 18 Republicans, voted to limit debate on the measure, comfortably surpassing a 60-vote threshold required for most legislation in the 100-seat Senate.

But unless all 100 senators consent to expedite the process, passage would have to wait until Monday or Tuesday under parliamentary rules that require legislation to move forward slowly and in stages.

“I said yesterday we could do this the easy way or the hard way,” Democratic Senate Majority Leader Chuck Schumer said on the Senate floor. “Yesterday, it appeared that some Republicans would like the Senate to do this the hard way. In any case, we’ll keep proceeding until we get this bill done.”

After the Senate passes the bipartisan bill, it would go to the House of Representatives, which Democrats also control by a narrow margin.

House Speaker Nancy Pelosi has repeatedly said she would only bring the bill to a vote after the Senate passes a separate $3.5 trillion bill providing funding to fight climate change and address home health care, which Democrats aim to push through without Republican votes using a maneuver called “reconciliation.”

Lawmakers in both parties have been working toward an agreement to consider a combination of Democratic, Republican and bipartisan amendments to the $1 trillion infrastructure bill under an expedited schedule.

The effort has been held up by opposition from Republican Senator Bill Hagerty, a freshman from Tennessee who objects to fast-tracking the legislation due in part to its effect on the federal budget deficit.

“I cannot participate in doing it this way,” Hagerty, who was former President Donald Trump’s ambassador to Japan, said on the Senate floor on Saturday.

Hagerty announced his opposition last week after the nonpartisan Congressional Budget Office said the legislation would increase the deficits by $256 billion over 10 years.

The CBO analysis did not include $57 billion in added revenue that Washington could collect over the long term from the economic growth benefits of infrastructure projects. It also did not count $53 billion in unused federal supplemental unemployment funds to be returned from states.

Hagerty showed no sign of wavering late on Saturday when he was approached on the Senate floor by several Republicans who fear that his opposition will prevent votes on amendments they believe could improve the legislation.

Republican U.S. Senator Kevin Cramer on Sunday defended his support of the bill, noting that it has broad public support and included several provisions that Republicans wanted, such as permitting reform for roads and bridges.

“We would like to get it through by Wednesday, preferably by Monday and, better yet, today if it’s at all possible,” he told Fox News’ “Sunday Morning Futures” program, arguing that by passing the bill, Republicans would make it harder for moderate Democrats to back the separate $3.5 trillion bill.

Despite Republican frustration, Democrats believe the deadlock on amendments poses no threat to the ultimate passage of the infrastructure bill.

“At the end of the day, this legislation is too important not to pass. Too important. Failure, as they say, is not an option,” Senator Tom Carper, Democratic floor manager for the bill, told reporters.

Reporting by David Morgan; Additional reporting by Ted Hesson, Chris Prentice and Susan Heavey; Editing by Scott Malone, Daniel Wallis and Alistair Bell