Shortly after congressional leaders met with Japan’s prime minister in Speaker Johnson’s ceremonial office in the Capitol on Thursday morning, the conversation turned to Ukraine aid.

Mr. Johnson was in the middle of another agonizing standoff with the ultraconservatives in his conference, after they had blocked legislation to extend a major warrantless surveillance law that is about to expire. His chief Republican antagonist, Representative Marjorie Taylor Greene of Georgia, had intensified her threat to oust him. But on Ukraine, he offered his counterparts an assurance.

“We’re going to get this done,” he vowed.

His comments, confirmed by multiple people familiar with the meeting, were consistent with what Mr. Johnson has been saying for weeks, both publicly and privately: that he intends to ensure the House will move to assist Ukraine, a step that many members of his party oppose.

Even as right-wing Republicans have sought to ratchet up pressure on their speaker, Mr. Johnson has continued to search for a way to win the votes to push through a Ukraine aid. He is battling not only stiff resistance to the idea among House Republicans, but also mounting opposition among Democrats to sending unfettered military aid to Israel given the soaring civilian death toll and humanitarian catastrophe unfolding in Gaza.

Mr. Johnson has yet to make any final decisions on how he plans to structure a new round of American military assistance to Ukraine.

Some Republicans have increasingly expressed interest in structuring the aid as a loan, an idea that Mr. Johnson has publicly floated and that former President Donald J. Trump previously endorsed. Mr. Trump raised again the idea again after a private meeting with Mr. Johnson at his Mar-a-Lago estate in Florida on Friday.

“We’re thinking about making it in the form of a loan instead of just a gift,” Mr. Trump said. “We keep handing out gifts of billions and billions of dollars and we’ll take a look at it.”

Mr. Johnson earlier this month floated bringing up the $95 billion emergency national security spending package for Ukraine and Israel passed by the Senate in February — and moving it through the House in tandem with a second bill containing policies endorsed by the conservative wing of his party, according to people familiar with the discussions.

That plan envisioned two consecutive votes — one on the Senate-passed bill, and another on a package of sweeteners geared toward mollifying Republicans who otherwise would be infuriated by Mr. Johnson’s decision to push through a bipartisan aid package for Ukraine. The second bill could include the REPO Act, which would pay for some of the aid by selling off Russian sovereign assets that have been frozen, as well as a measure forcing President Biden to reverse a moratorium on new permits for liquefied natural gas export facilities. It could also include some kind of border security measure.

Mr. Johnson’s task at hand is to cobble together an increasingly elusive coalition of mainstream Republicans and Democrats who will support the Senate-passed bill.

Some liberal lawmakers have signaled opposition to approving additional aid for Israel after a strike by the Israeli military that killed seven aid workers in Gaza. At the same time, a growing number of Republicans view approving another aid package for Kyiv as toxic with their voters.

Mr. Johnson is toiling to navigate those dynamics with his own job on the line. Ms. Greene has long said she would seek to oust him were he to bring up legislation to aid Ukraine without securing sweeping policy concessions from Democrats on the border. And ultraconservatives were enraged at him on Friday when he broke with custom and cast a decisive vote to kill a proposal that would have required U.S. officials to obtain warrants before searching the messages of Americans swept up by the warrantless surveillance program.

Mr. Johnson nodded to the challenges at a news conference on Wednesday, saying he was sifting through “a lot of different ideas” raised by his colleagues for aiding Ukraine.

“It’s very complicated matter, and a very complicated time,” he said. “And the clock is ticking on it and everyone here feels the urgency of that. But what’s required is that you reach consensus on it.”