Why Trump's imminent return might scuttle Biden's last plays in foreign wars

President Joe Biden will see out his term knowing that President-elect Donald Trump -- a man he fought desperately hard to unseat in 2020 and called a "genuine danger to American security" -- will succeed him.

Foreign policy has been central in Biden's long political career. It will likewise form a major chunk of his legacy, as will the two wars -- Russia's invasion of Ukraine and the Middle East conflagration sparked by Hamas' Oct. 7 attack -- that erupted during his term.

Now less encumbered by political calculations -- for himself or for Vice President Kamala Harris -- and with only two months until Trump's second inauguration, the outgoing president may have one last window to wield the power of the Oval Office in both theaters.

But with Trump looming above the outgoing Biden-Harris administration, American allies and enemies may be hesitant to engage with the outgoing administration.

European nations, for example, are already shifting focus to how best to court Trump, Leslie Vinjamuri of the British Chatham House think tank told ABC News.

"All these European leaders are very quickly reaching out," she added. "They're congratulating him. They want to talk with him. They want to work with him, because they understand that the stakes are extremely high and they clearly feel that by talking with him, they have an ability to influence policy and the outcome."

"What they don't want to do is to be seen to be making a deal with Joe Biden that undercuts whatever it is that Trump is going to do," Vinjamuri added.

"It's a very tricky position to be in, because if anything's visible that cuts across what he wants to do, you as a leader risk being punished."

Those at the top of American politics know that foreign policy success can accelerate careers and define legacies. Former President Richard Nixon infamously undermined President Lyndon B. Johnson's efforts to negotiate an end to the Vietnam War during the 1968 election campaign for fear it would reduce his chances of victory.

Though he has already secured his second term, Trump appears unlikely to help the Biden administration with any foreign policy "wins" in its closing days.

"There's a lot of uncertainty and room for maneuver -- it's highly unpredictable," Vinjamuri said.

Russia and Ukraine

Russia's war on Ukraine has dominated much of Biden's presidency. He will leave office with Moscow's forces holding large parts of Ukraine and still advancing, even if slowly and at huge cost.

"I think that now Biden can be much more decisive in support of Ukraine, especially when he sees that Trump will be the next president," Oleksandr Merezhko -- a member of Ukraine's parliament and the chair of the body's foreign affairs committee -- told ABC News.

"Biden has his hands completely untied," Merezhko added. "Now Biden is thinking about his legacy."

"He might even try to take some decisions which will make irreversible changes in support of Ukraine -- for example, he might lift all the restrictions on the use of the Western weapons on the territory of Russia," Merezhko said. "And he might start the process of inviting Ukraine to join NATO."

Merezkho acknowledged that progress on the NATO front might be ambitious. "Yes, he doesn't have much time," he said. "But he -- with [National Security Adviser] Jake Sullivan and [Secretary of State] Antony Blinken -- might do something creative to help Ukraine."

It appears unlikely that Biden's final months will bring Kyiv any closer to NATO membership. Ukrainian leaders are still pushing for an invitation to join the alliance despite fierce opposition from Russia -- and hesitance among key alliance members. Allies have repeatedly said that "Ukraine's future is in NATO," but even top officials in Kyiv acknowledge this cannot happen amid war with Moscow.

The outgoing president may at least be able to ring fence much-needed funding for Kyiv.

Matthew Savill of the Royal United Services Institute think tank in the U.K., said Biden "might choose in his last months in office to use the remainder of the funding available for support to Ukraine under Presidential Drawdown Authority, amounting to over $5 billion."

The Pentagon has already committed to rolling out new funding packages between now and January totaling some $9 billion. "That is consistent with how we've been doing this in the past," Pentagon spokesperson Sabrina Singh told journalists last week. "It's something that we've done on a pretty regular, almost weekly, basis."

Biden has also reportedly already decided to allow non-combat American defense contractors to work in Ukraine to maintain and repair U.S.-provided weaponry.

Yehor Cherniev -- a member of the Ukrainian parliament and the chairman of his country's delegation to the NATO Parliamentary Assembly -- told ABC News that deeper sanctions on "Putin's inner circle" are on Kyiv's wish list, along with the delivery of all previously allocated aid, commitments for more, plus the end to restrictions on Western weapon use inside Russia.

Trump has suggested he would quickly end Russia's invasion by threatening to cut off military aid to Kyiv unless it agrees to hand Moscow direct or indirect control of swaths of occupied territory in the south and east of the country.

As such, his election has raised concerns in Ukraine of an imminent sellout.

Merezhko, though, stressed the unpredictability of the president-elect. "Trump might become even more critical of Russia to show that all suspicions about him are groundless," he said.

"We know that Trump loves his country and seeks to protect its interests in accordance with his vision," Cherniev said. "Therefore, we are confident that the U.S. will not leave us alone with Russia, since this is not in the interests of the U.S. and the free world."

"However, much will depend on Putin's willingness to make concessions and compromises," he added. "If the Russian dictator does not show due flexibility, I think Trump will increase his support for Ukraine."

As to potential tensions between Trump and Biden in the coming months, Merezhko said, "Competition between them will continue."

"For us, it would be better if they compete amongst themselves on who will do more for Ukraine."

European nations, meanwhile, will be bracing for Trump while hoping to influence the president-elect's take on the war.

Vinjamuri, of the Chatham House think tank, said Europeans will also be working closely with the Biden administration "to put in place everything that they can to keep Europe and Ukraine in as good a place as possible before Jan. 20, when Trump comes in and tries to negotiate a peace deal."

"That means that getting Ukraine in the best position on the ground, because when you start negotiating a peace, a lot of what gets locked in is based on what land people hold," she said.

The Middle East

The Biden administration's pre-election Middle East diplomatic push does not appear to have made significant breakthroughs in either Gaza or Lebanon. Fierce ground fighting and devastating Israeli airstrikes continue on both fronts, with the toll of civilian dead and displaced growing ever larger.

The regional war began with Hamas' Oct. 7, 2023, attack, which killed around 1,200 people in southern Israel and saw around 250 taken back to Gaza as hostages. Israel's military response in the strip has killed some 43,600 people and injured more than 102,000, according to the Hamas-run Gaza Health Ministry. Israel's airstrike and ground campaign in Lebanon has killed more than 3,000 since Oct. 8, 2023, Lebanese health officials say.

Israeli Prime Minister Benjamin Netanyahu replaced Defense Minister Yoav Gallant -- one of his prime political rivals and an advocate for a cease-fire deal -- on the eve of the U.S. election, reinforcing his position and entrenching his government's commitment to what he has called "total victory."

Hafed Al-Ghwell, senior fellow and executive director of the North Africa Initiative at the SAIS Foreign Policy Institute, Johns Hopkins University, told ABC News he has little expectation of peace during Biden's final months. "I don't think he has any incentive to do anything," Hafed said.

"In the case of Israel and Palestine, Biden has taken not just a political stand but an ideological one, and there is no sign that he is going to change that," Hafed added. "He has called himself a Zionist, and he had ample opportunity to stop this war. Even when the United Nations proposed a resolution to end the occupation, he didn't support it."

"It would be really controversial for an outgoing president to make any major decisions," he continued.

Meanwhile, Netanyahu will be confident in the new White House's backing in his suppression of Palestinian and Lebanese groups, as well as in his wider showdown with Iran.

Netanyahu "probably feels like he has a free run," Vinjamuri said. "Even if Biden tried to push him, I'm not so sure he would be responsive, because he knows that Trump is now coming into office."

Hafed suggested Netanyahu's domestic concerns, too, will be driving his policy in the coming months. "He knows that the minute this war stops, the Israeli public won't want him around," he said. "So, he will continue the war in Lebanon and probably threaten Iran, knowing he will have the full support of Trump."

Burcu Ozcelik at RUSI said the extent of Trump's influence over Netanyahu tops "a complex list of unknowns."

"Trump in recent weeks indicated that he was prepared to give Israel freer rein, provided that the war ended by the time he entered office," he added.

Those living in the region will be left grappling with the fallout, Hafed continued. "For the people of the Middle East, Biden's legacy is one of a bloodbath," he said. "The region is bitter and battered."

ABC News' Luis Martinez contributed to this article.