He shunted aside a bipartisan law, signed just weeks ago, imposing new tariffs on Russia. He cut a deal to purchase diesel from Moscow. His negotiators agreed on the vague outlines of a deal for much of Lukoil, a battered Russian energy firm. And he called for the replacement of President Volodymyr Zelensky of Ukraine, whose success in taking the fight inside Russia deeply frustrates him.

President Trump’s intensifying effort in the past few weeks to rehabilitate Russia and usher President Vladimir V. Putin back into diplomatic society is remarkable for its speed, its characterization of Mr. Zelensky as the primary obstacle to peace, and its brazen denial that Russia is continuing the war that Mr. Trump says he is trying to end.

“Russia, frankly, has been fine on Ukraine,” Mr. Trump said on Monday, speaking to reporters outside the White House as he left for a campaign rally. “They haven’t been doing much,” he said, making no mention of the Russian missiles and jet-powered drones that have been targeting apartment buildings in Kyiv and Ukraine’s surviving electricity grid.

In contrast, he said, “We’ve given a lot to Ukraine. They’ve given nothing to us. Remember that.” He repeated the statement for emphasis. The night before, he wrote on social media that Mr. Zelensky “doesn’t want to end this war, and probably never did,” because it brought him a flow of cash and arms from Europe, making no mention that Ukraine is fighting for its sovereignty and even survival in a war that it did not start.

Mr. Trump’s disdain for Mr. Zelensky is hardly new. Nor is his willingness to give the benefit of the doubt to Mr. Putin, for whom he has often expressed respect and even admiration.

But what is different now is Mr. Trump’s increased determination to force a deal on Mr. Zelensky, telling him that holding out to retain occupied portions of the country’s eastern provinces is not worth it — and that there is money to be made for Ukraine, as well, if it would only drop its objections to an accord, even one written largely on Russia’s terms.

That will be the American message to Mr. Zelensky on Tuesday in Oslo, where Mr. Trump’s special envoy, Steve Witkoff, and his son-in-law, Jared Kushner, are expected to meet the Ukrainian president.

Participating in the discussion, officials say, will be Norway’s prime minister, Jonas Gahr Store, and Alexander Stubb, the president of Finland. (Finland has become an enthusiastic member of the NATO alliance, but in World War II it ceded about 12 percent of its territory to Russia, and has never gotten it back.)

The next day Mr. Witkoff and Mr. Kushner will fly to St. Petersburg, Russia, to meet Mr. Putin in his hometown. There, Mr. Trump’s representatives are expected to take the next step in their efforts to show the benefits of deal-making with Mr. Putin by securing the release of a long-held American.

Mr. Trump discussed the prospect of a hostage release again on Monday, but did not say who was involved. The only American the State Department categorizes as “wrongfully detained” in Russia is Stephen Hubbard, who Russia accused of fighting as a mercenary for Ukraine when he was seized in 2022. Mr. Hubbard, who is in his mid-70s, was sentenced to more than six years in a penal colony.

The timing of the release, if it happens, says volumes about Mr. Putin’s strategy. Ridding Russia of an elderly American hostage costs Mr. Putin nothing, and does no good for Ukraine. But in the midst of midterm elections in the United States it allows Mr. Trump to make the case that he is pursuing an America First foreign policy, complete with the heartwarming images of a prisoner being reunited with his family.

But the larger goal here, for Mr. Putin and Mr. Trump, is to normalize a relationship that began to go off the rails more than a decade ago, when Mr. Putin took Crimea, a territory that was integrated with Ukraine during the Soviet era, and when he began to send Russian fighters into eastern Ukraine.

Europe and the United States responded with sanctions. But a year later, then- Chancellor Angela Merkel of Germany signed a deal with Mr. Putin to build the Nord Stream 2 gas pipeline, calling the Russian leader a “reliable supplier.”

The idea was to reintegrate Russia with the West, in hopes of curbing Mr. Putin’s territorial appetites. The effort failed; seven years later Russia launched its full invasion of Ukraine.

Today, that history, and the rationale behind it, is replaying itself. But it is Mr. Trump who is taking the role that Ms. Merkel once played.

Mr. Trump’s ambitions are clearly bigger. There is already talk of a three-way meeting in China between Mr. Trump, Mr. Putin and Xi Jinping of China on the sidelines of a larger summit of Pacific Rim countries scheduled for next month. Mr. Trump said on Monday the goal would be to discuss the three largest nuclear arsenals in the world, and “denuclearization.” (He likely meant arms control, since none of the three powers seems remotely interested in eliminating their nuclear stockpiles.)

That is exactly what Mr. Putin has in mind: Expanding the discussion with the United States to other topics, apart from Ukraine, that make the long-running conflict look like just one of many issues to be managed. And should the three-way meeting happen, the image of the leaders of the three largest nuclear powers talking would likely carry the suggestion that they are carving the globe into zones of influence, much as Stalin, Churchill and Franklin D. Roosevelt did at Yalta.

A month later the three are scheduled to be together again, this time at a G20 summit meeting at Mr. Trump’s Doral resort in Florida. Several months ago, Mr. Trump invited Mr. Putin to attend, the first indication that the Russian leader was being called back in from the cold.

To get to that point, however, Mr. Trump had to abandon all talk of helping Ukraine defend a fledgling, if still corruption-plagued, democracy. While he insists that any settlement of the war would come with “security guarantees” to keep Russia from re-invading, Ukrainian officials say they now doubt that the United States would really come to their aid, at least while Mr. Trump is in office.

“The reason it’s hard to think of a precedent of America switching sides in a conflict like this is that there really isn’t one,” said Richard Haass, a longtime diplomat who served Republican and Democratic administrations from the end of the Cold War through the invasion of Iraq 23 years ago.

“What’s unprecedented here is the decision to reverse course and penalize the victim of the invasion — Ukraine — while rewarding the aggressor.”

In fact, as Mr. Haass suggests, there is no satisfying analogy in recent history.

Yes, Nixon shocked allies in 1972 with his opening to China, which led, years later, under President Jimmy Carter, to diplomatic recognition of the People’s Republic, and the withdrawal of formal diplomatic relations with Taiwan. But there was no active war when Nixon made the move, and it came with extensive commitments from Washington to protect Taiwan, a strategy that has worked, so far, for nearly half a century.

The United States pulled out of Vietnam, but while it had extensive disputes with South Vietnam it did not openly side with the North. And Mr. Trump, in his first term, and then President Joseph R. Biden Jr., negotiated and executed a deal with the Taliban that quickly led to the takeover of Afghanistan — again, a withdrawal that resulted in the collapse of a government that the U.S had tried to prop up. But there have been no business deals brewing with the Taliban leadership.

Mr. Trump’s aides insist that the war between Russia and Ukraine is now at what they call an “inflection point.” The next move is Mr. Zelensky’s, they insist, saying he must prove to Mr. Trump that he, too, is willing to deal with the Russians, even if it means giving up sovereign territory.

That is something the Ukrainian leader once promised to Congress that he would never do. He got a standing ovation in return, and promises that American support would never flag. On Sunday, appearing on NBC’s “Meet the Press,” he acknowledged that the atmosphere was different. Asked if his country could survive without American military and intelligence aid, he responded: “Of course, in all the difficult situations, you have a chance. But we will have a low chance — low chance to survive without support of the United States.”