European and Ukrainian officials are concerned that Donald Trump is on the verge of deviating from the brink of peaceful negotiations with Kiev and Moscow, which could use smaller progress in negotiations as an "excusation" saying his work is done.

The U.S. president was elected as a promise to end the war in "24 hours", but his proposal to Russia's Vladimir Putin and attempted to be strong Ukrainian leaders to win support for his initial 30-day ceasefire proposal, not to mention a lasting battle.

After talks with the U.S. side in recent days, European and Ukrainian officials are convinced that Trump is ready to seize any breakthrough this week, marking the first 100 days of his tenure, even if there is no long-term solution, four officials told the Financial Times.

A European official said Trump “established a situation where he gave himself the excuse to walk away and leave it to Ukraine and us (Europe) for repair.”

They added that Putin's reluctance to agree with key U.S. and Ukraine's demands, such as maintaining post-war Ukrainian military power, and the complexity of the conflict, has caused Trump to reassess his commitment to a peace deal.

U.S. Secretary of State Marco Rubio called it a "critical" week of negotiations Sunday and said Washington was unwilling to be dragged into an extended negotiation.

The Russian president on Monday offered a three-day ceasefire during a holiday from May 8 to 10, when Russia celebrated the victory of the Soviet Union in World War II - but he failed to retain his previous commitment to cease hostilities on Easter and Ukrainian energy infrastructure.

One briefing discussion said U.S. officials were "worrying that they were really back in conversations with Russia" and began floating an idea of ​​a deal that could fit Trump's quick schedule.

However, Trump's efforts to end the war quickly were related to Putin's ignorance and agreed not to meet his maximum demands, such as "depreciating" Ukraine.

"Some people think the Russians may keep moving forward," the person said. "In fact, some elements are good, but now what to do is an impatient question."

Trump praised his Ukrainian rival Volodymyr Zelenskyy over the weekend, who met him at the funeral of Pope Francis in the Vatican on Saturday. He also criticized Putin, saying he was "surprised and disappointed" by the Russian missile attack in Ukrainian cities.

But some Ukrainian officials told the British KMT that they were worried about the U.S. president walking away, and a senior official said he thought it was a "serious possibility."

However, Ukrainian Foreign Ministry spokesman Heorhii Tykhyi said the meeting between the presidents was "constructive and a good person".

After a public quarrel between Trump and Zelenskyy in the Oval Office in February, Ukrainian officials said they experienced whipping after a positive encounter, only surprised when their American counterparts returned to Washington.

Shortly after the Vatican meeting, Trump published an article on his Truth Society Platform in encouraging Kiev, where he threatened Russia to adopt new sanctions to include it in negotiations.

But a day later, Trump's Secretary of State Rubio poured cold water on the idea of ​​more trade restrictions, which he said would prolong the war.

"This week will be a very important week and we have to determine if this is an effort we want to continue to be involved," Rubio told NBC.

Tykhyi dismissed the comments, saying Kyiv believes they are "part of the communication strategy." "Obviously, as mediators, the United States is trying to push for peace (in Ukraine and Russia) direction, and that's how we read these statements."

On Monday, Russian and Foreign Minister Sergei Lavrov said that Moscow believes that Moscow's "international recognition" of the annexation of five Ukraine regions is a "highest priority" for any transaction.

All these developments have caused some European capitals to rethink their efforts to "keep (Trump) involved" and instead "do the right thing, not what Trump wants."

Kiev began quietly preparing to do it alone by increasing domestic weapons production and talking to European allies about future aid.

Officials say it is unclear whether the U.S. will stop intelligence and military support for Ukraine, as Trump did in March — amid the White House withdrawing from diplomatic efforts.

"There are serious concerns in Ukraine that Trump may leave the ceasefire negotiations," said Oleksandr Merezhko, a member of the ruling party of Zelenskyy and head of the parliamentary Foreign Affairs Committee.

"The worst thing that could happen in Ukraine relations in the Ukraine is that Trump will lose any interest," he said, adding that Putin may think it is the default license for the war to escalate."

Other reports from Andy Bounds in Brussels and Guy Chazan in New York