WASHINGTON — The Senate is plodding past right-wing Republican opposition to helping Ukraine fight Russia, working through the weekend on a $95.3 billion military aid package for Kyiv, Israel and other allies that could be President Biden’s last chance for now to deliver substantial American support.

Senators conducted a late-night vote Friday, advancing to next steps as they spin through objections from a core group of Republicans. More closely aligned with President Trump, the GOP’s 2024 front-runner, the Republican senators aren’t putting a priority on stopping President Putin’s invasion.

Senator Schumer told colleagues he would be willing to amend the package to win over more support, but the New York Democrat also warned they would stay in session “until the job is done.”

Even if the foreign aid package gets off the ground in the Senate with possible Sunday voting, the package still faces a deeply uncertain future in the House. In that chamber, the Republican majority is even more hostile to helping the American ally in Europe, as the war enters its second year.

Attendance slipped Friday night as senators advanced the bill, 64-19, with 14 Republicans joining Democrats to move it forward.

Overall, the bill includes $14.1 billion in military aid for Israel for the war with Hamas, $8 billion for the Republic of China on Taiwan and partners in the Indo-Pacific to counter China, and $9.2 billion in humanitarian assistance for Gaza, among other provisions.

 It had stalled out for weeks, but is on track toward passage in the days ahead after a separate American border security deal collapsed when Republicans rejected it.

Central to the package has always been the military aid for Ukraine, whose President Zelensky has visited Congress to plead for help, including in a whirlwind trip last December, as he tries to preserve his country.

Amid shortages on the battlefield, the package would unleash $60 billion for Ukraine, mostly to purchase American-made defense equipment, including munitions and air defense systems that authorities say it desperately needs as Russia batters the country. It includes $8 billion for the government in Kyiv and other assistance.

Mr. Biden, speaking with the German chancellor on Friday at the White House, said it would be “close to criminal neglect” if Congress fails to stand by its European ally.

“The failure of the United States Congress, if it occurs, not to support Ukraine, is close to criminal neglect,” Mr. Biden said. “It is outrageous.”

The resistance from the Republicans to helping Ukraine has been an intensifying about-face for the party that once defined itself on a muscular foreign policy. In the Trump era, the GOP has latched on to a more isolationist approach, echoing his “America First” agenda with a more ambivalent attitude toward Putin’s aggression.

In a key vote Thursday, 17 Republican senators agreed to start debate on the bill — but 31 voted against it.

“Our job first and foremost is to protect this country,” Senator Lee of Utah, a leading opponent, said during a Friday night speech.

Senator McConnell, who has been critical of Mr. Biden’s handling of Ukraine and other national security issues, is nevertheless pushing past the isolationists in his party to marshal the national security package to passage.

Mr. McConnell has visited Mr. Zelensky at Kyiv and hosted the leader at the Capitol, and the Republican leader has tried to impress on his party the importance of investing in allies — and replenishing the American industrial base that manufactures the weaponry being used to push back Russia.

“This is about rebuilding the arsenal of democracy and demonstrating to our allies and adversaries alike that we’re serious about exercising American strength,” Mr. McConnell said.

During Friday night’s floor debate, Senator Sullivan of Alaska, who served in the military as a Marine, emphasized most of the money goes “to build weapons, to build ammo” in states all across the country with what he said would be thousands of American jobs.

“This is a generational investment in our ability to defend ourselves,” Mr. Sullivan said.

Senators groused that at least one Republican, Senator Paul of Kentucky, was forcing the time-consuming procedural steps as often happens to register opposition.

To draw in political support, the Senate leaders stripped out some economic assistance for Ukraine that many Republican senators objected to, leaving that to allies in the European Union, who overcame their own political opposition last week to approve an aid package.

Bundling the American package with aid to Israel and Indo-Pacific allies has won over some Republicans, but has also drawn concerns from some Democrats about the aid going to support Israel’s war against Hamas.

“I cannot find words,” Senator Sanders, the independent from Vermont, said during a speech Friday. “This is American complicity at its worse and it’s really quite unbelievable,” Mr. Sanders said. 

Senator Van Hollen of Maryland and other Democrats announced they had secured a national security memorandum with the Biden administration to ensure the assistance is used in accordance with international and humanitarian law.

The Senate is not expected to take votes Saturday, but senators, who are on the brink of a two-week recess away from Washington, are expected back midday Sunday, ahead of the Super Bowl, to push the package toward final votes.

The package would go to the House next, but Speaker Johnson has not indicated if, or when, he would schedule any votes on it.