Europe is working quickly to mend the rift between Ukraine and the United States.

With Britain and France forming a “coalition of the willing” to devise a strategy for resolving Ukraine’s conflict with Russia, European leaders rushed on Sunday to mend Ukraine’s strained ties with the United States. They are hoping that a skeptic like President Trump will support their endeavor.

The leaders, who gathered in London at the request of British Prime Minister Keir Starmer, pledged to increase backing for Ukrainian President Volodymyr Zelensky following his acrimonious confrontation with Mr. Trump last week. However, a number of people also voiced optimism that the two may mend their rift, highlighting Europe’s hesitancy to rupture a transatlantic partnership that has maintained peace for eight decades.

Mr. Starmer stated that he thought Mr. Trump was dedicated to a long-term peace deal between Russia and Ukraine, even if he was upset with Mr. Zelensky in the Oval Office on Friday. He stated that Britain and France will work with Mr. Zelensky to create their own proposal in collaboration with other European nations.

Although the plan’s specifics were vague, Mr. Starmer said the Europeans might use it as a starting point to convince Mr. Trump to agree to American security assurances. Britain and France are attempting to recruit additional nations around Europe and have already committed to provide soldiers to a peacekeeping mission.

Two weeks after Mr. Trump’s unexpected outreach to Russian President Vladimir V. Putin, his remarks encapsulated the predicament facing Europe. In a possible peace agreement mediated by Trump, neither Europe nor Ukraine now have a place at the table. Furthermore, Mr. Trump has not committed to provide any security guarantees to stop Russia from attacking its neighbor once more.

The rift widened when Mr. Trump and Mr. Zelensky had a heated argument. Mr. Starmer, who had his own, considerably more amicable encounter with Mr. Trump the day before, said that no one was interested in seeing what transpired last Friday.

The prime minister has attempted to act as a mediator between Mr. Trump and Mr. Zelensky. According to a senior British source, he suggested to both men over the phone following their altercation that Mr. Zelensky should come to the White House on Friday night in order to patch things up with the president.

According to the official, who spoke on condition of anonymity due to the delicate nature of the matter, both leaders backed down, stating that it would be best to let tensions to subside and the air to clear. However, Mr. Zelensky has also stated that he believes his disagreement with Mr. Trump can be resolved.

Europe embraced Mr. Zelensky warmly on Sunday in London. The 18 leaders in attendance, including French President Emmanuel Macron, German Chancellor Olaf Scholz, Italian Prime Minister Giorgia Meloni, and Canadian Prime Minister Justin Trudeau, all made signs of solidarity for him.

Mr. Zelensky then took a plane to Sandringham, King Charles III’s rural home northeast of London, to see him. That visit, which was requested by Mr. Zelensky, had symbolic significance since Mr. Starmer had personally given Mr. Trump a unique invitation from the monarch to visit Britain as a state visitor for the second time.

As a result, European nations will have to bear a far greater weight of defending the continent. Mr. Starmer urged nations to increase military expenditure in line with Britain. NATO Secretary General Mark Rutte claimed a number of nations have committed to doing so, but he would not identify them.

Following his discussion with Mr. Zelensky on Saturday, Mr. Starmer granted Ukraine a loan of 2.26 billion pounds, or around $2.8 billion, to purchase military equipment. He said on Sunday that Ukraine will be able to purchase more than 5,000 sophisticated air defense missiles using 1.6 billion pounds ($2 billion) in British export funding.

Ursula von der Leyen, the president of the European Commission, stated that the European Union will provide Ukraine with military and economic support in an effort to make it “a steel porcupine that is indigestible for potential invaders.”

Mr. Starmer has been thrown into a situation that is unfamiliar for a British prime minister: the center of Europe in the midst of a crisis, due to the conflict in Ukraine. The fast evolving security environment is bringing Britain closer to the European Union, more than eight years after the country chose to leave.

The bloc’s high representative for foreign affairs and security policy, Catherine Ashton, a British national, stated that Mr. Starmer’s successful encounter with Mr. Trump had strengthened his reputation as a European leader.