WASHINGTON / MOSCOW - US President Donald Trump said on Sunday that Ukrainian President Volodymyr Zelensky could swiftly end the conflict with Russia by abandoning efforts to reclaim Crimea and forgoing NATO membership.

In a Truth Social post, Trump said, "President Zelensky of Ukraine can end the war with Russia almost immediately, if he wants to, or he can continue to fight." "No getting back Obama given Crimea...and NO GOING INTO NATO BY UKRAINE. Some things never change!!!"

Earlier, Trump shared a social media post from his supporter, which said, "Ukraine must be willing to lose some territory to Russia otherwise the longer the war goes on they will keep losing even more land!"

ALSO READ: Putin says Russia wants to see Ukraine conflict end

Also on Sunday, US Secretary of State Marco Rubio told ABC News' This Week that both Russian President Vladimir Putin and Zelensky must make concessions to achieve a peace deal.

In a separate interview with Fox News, Rubio said that European leaders involved in talks with Ukraine "are very helpful being in the room sometimes," particularly in providing long-term security guarantees for Ukraine.

Rubio said he hoped the Europeans would also help to push Ukraine toward a potential peace deal by "giving ideas about what accommodations can be made."

Meanwhile, Rubio did not rule out the United States imposing more sanctions on Russia. In an appearance on NBC's Meet the Press, he said doing so would signal the failure of Trump's efforts to reach a ceasefire or lasting peace in Ukraine. "The minute he takes those steps, all talks stop," he said.

READ MORE: Trump, Putin say Alaska meeting 'constructive'

Presidential envoy Steve Witkoff said the White House extracted critical wins from its Friday meeting with Putin in Alaska.

Security guarantees offering Ukraine "Article 5-like protections" are the real prize, Witkoff said Sunday on CNN's State of the Union. They're "game-changing," he added.

"We got to an agreement that the United States and other European nations could effectively offer Article 5-like language to cover a security guarantee," Witkoff said.

"We didn't think that we were anywhere close to agreeing to Article 5 protection from the United States in legislative enshrinement within the Russian Federation, not to go after any other territory when the peace deal is codified," he added.

Article 5 protection generally refers to the collective defense provision within NATO, which states that an attack against one ally is considered as an attack against all allies.

On Friday, a Trump-Putin meeting was held in Anchorage, Alaska, with no deal reached. Zelensky will travel to Washington, alongside a number of major European leaders, to meet with Trump on Monday.

"At the request of President Zelensky, I will join the meeting with President Trump and other European leaders in the White House tomorrow," European Commission President Ursula von der Leyen said Sunday on X.

READ MORE: European leaders, Zelensky to meet Trump in Washington

At a later press conference with Zelensky in Brussels, von der Leyen said the EU welcomed Trump's willingness to contribute to Article 5-like security guarantees, adding that it was essential to have a trilateral meeting between the presidents of Russia, Ukraine and the United States "as soon as possible."

Crimean Bridge

Russia's Federal Security Service (FSB) foiled an attempt by Ukrainian special services to attack the Crimean Bridge with a car packed with explosives, local media reported Monday.

The vehicle, carrying a powerful improvised explosive device, was transported into Russia from Ukraine through several transit countries. It entered Russia via the Verkhny Lars checkpoint on the Georgia-North Ossetia-Alania border, and was bound for the Krasnodar region on a car carrier driven by a private freight driver, said the FSB, cited by RIA Novosti.

RIA Novosti did not provide a timeline for these moves in its report.

The car had been planned to be handed over to another driver, who was supposed to drive it across the Crimean Bridge, unknowingly becoming a suicide bomber, the report said.

"FSB officers managed to uncover their plans in time, detect and neutralize the explosive device concealed inside a Chevrolet Volt car, and detain all those involved in transporting it into Russia," the FSB said.