WASHINGTON, Aug 8 (Reuters) - The U.S. Senate will try to move toward passage of a $1 trillion infrastructure bill on Sunday, as Republicans struggle to heal a rift within their ranks that has inhibited party efforts to amend the legislation. The Senate was scheduled to convene at noon EDT (1600 GMT) and was expected to hold two procedural votes on Sunday evening, unless Republicans and Democrats could reach an agreement on amendments that would allow the chamber to move more quickly to passage. The legislation represents the biggest investment in decades in America’s roads, bridges, airports and waterways, and its passage through the evenly divided Senate would represent a major victory for President Joe Biden and a group of bipartisan lawmakers who spent months crafting the measure. 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. Lawmakers in both parties have been working toward an agreement to consider a combination of Democratic, Republican and bipartisan amendments under an expedited schedule. But 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, declared 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 here 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 a number of Republicans who fear that his opposition will prevent votes on amendments they believe could improve the legislation. “Impasse. That’s the headline: impasse. There’s nothing below that,” Republican Senator John Cornyn later told reporters. Despite Republican frustration, Democrats believe the deadlock on amendments poses no threat to 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; Editing by David Gregorio) Our Standards: The Thomson Reuters Trust Principles.