The Senate voted 64-19 to advance the legislation one step along a chain of preliminary votes that could stretch into next week, unless party leaders can reach agreement with rank-and-file lawmakers to fast-track the bill. Lawmakers expect to take the next procedural step in a rare Sunday session.

In Friday's vote, the bill cleared a simple majority threshold with 14 Republicans supporting the measure.

Many Republicans want to make a deal with Senate Majority Leader Chuck Schumer, a Democrat, to allow amendments to the legislation in exchange for quicker action.

But other Republicans, who reject the bill's $61 billion in Ukraine aid, have vowed to delay consideration for as long as possible by forcing the Senate to comply with a labyrinth of time-consuming parliamentary rules.

Republicans had insisted that Ukraine aid be accompanied by provisions to secure the U.S.-Mexico border, only to reject a bipartisan border agreement once former President Donald Trump, the party's presidential frontrunner, came out against the deal.

Some of those same lawmakers now hope to offer their own amendments to stem the flow of migrants into the United States, while others want to forgo humanitarian assistance provisions and restrict foreign aid to weapons and materiel.

If the legislation ultimately passes the Senate, it will face an uncertain future in the Republican-controlled House of Representatives, where Speaker Mike Johnson has indicated he could split the aid into separate bills.

"We'll see what the Senate does," Johnson told reporters this week. "I've made very clear that you have to address these issues on their own merits."

Johnson spoke a day after the House rejected a stand-alone aid bill for Israel.

(Reporting by David Morgan and Richard Cowan; editing by Jonathan Oatis)

By David Morgan