KYIV, Ukraine — Senior military officers from more than two dozen countries across Europe and beyond met in England Thursday to flesh out plans for an international peacekeeping force for Ukraine as details of a partial ceasefire are worked out.

U.K. Prime Minister Keir Starmer said he didn’t know whether there would be a peace deal in the Russia-Ukraine war, but “we are making steps in the right direction" as a “coalition of the willing” led by Britain and France moves into an “operational phase.”

“We hope there will be a deal but what I do know is if there is a deal, the time for planning is now,” he said during a visit to the meeting of military planners at a British base in Northwood, just outside London. “It’s not after a deal is reached.”

“It is vitally important we do that work, because we know one thing for certain which is a deal without anything behind it is something that (Russian President Vladimir) Putin will breach," he said.

Ukraine and Russia agreed in principle Wednesday to a limited ceasefire after U.S. President Donald Trump spoke with the countries’ leaders this week, though it remained to be seen when it might take effect and what possible targets would be off limits to attack.

Ukrainian President Volodymyr Zelenskyy, speaking in Norway on Thursday, said that although he originally had sought a broader ceasefire, he was committed to working with the U.S. to stop arms being directed at power production and civilian facilities.

“I raised this issue with President Trump and said that our side would identify what we consider to be civilian infrastructure,” Zelenskyy said. “I don’t want there to be any misunderstanding about what the sides are agreeing on.”

‘Shuttle diplomacy’ expected after Saudi Arabia talks

The tentative deal to partially rein in the three-year war came after Putin rebuffed Trump’s push for a full 30-day ceasefire. The difficulty in getting the combatants to agree not to target one another’s energy infrastructure highlights the challenges Trump will face in trying to fulfill his campaign pledge to quickly end the war.

Negotiators from Moscow and the U.S. will meet Monday in Riyadh, Saudi Arabia, Putin's foreign affairs adviser Sergei Ushakov told Russian news agencies.

Zelenskyy said his team would also meet with the U.S. in Saudi Arabia to discuss technical issues, and then the U.S. will act as an intermediary running “shuttle diplomacy” between Kyiv and Moscow.

Despite the negotiations, hundreds of drone attacks were launched overnight by both sides, injuring several people and damaging buildings.

Ukraine said Russia had launched 171 long-range drones and it shot down 75 while another 63 decoy drones disappeared from radar after likely being jammed. Russia said it destroyed 132 Ukrainian drones in six Russian regions and the annexed Crimea.

Kropyvnytskyi, a city in central Ukraine, faced its biggest attack of the war as about four dozen drones injured 14 people, including a couple with serious burns, and damaged houses and apartments.

"In a cruel twist, enemy drones hit Myru Street (‘Peace Street’ in English),” Andrii Raikovych, head of the regional administration, said.

More than 50 drones were intercepted in Russia's Saratov region — the largest attack of its kind in the area — shattering windows in a hospital and damaging two kindergartens, a school and about 30 homes, Gov. Roman Busargin said. The attacks were focused on Engels, an industrial city near Russia's main base for nuclear-capable strategic bombers.

Battlefield losses mount, though official numbers elusive

In its latest estimate, the U.K. Defense Ministry said Russian troops suffered 900,000 casualties — including up to 250,000 killed — since Moscow’s invasion of Ukraine three years ago. That’s a jump of 200,000 from a fall estimate.

Western estimates of the parties’ war losses have varied and couldn’t be independently verified.

War losses have been a tightly guarded secret in Russia. The Defense Ministry’s most recent figures were from 2023 when it reported 6,000 deaths, which was regarded as unreliable.

The U.K. did not release a similar estimate for Ukrainian casualties.

Zelenskyy told NBC News last month that more than 46,000 Ukrainian soldiers had been killed, and more than 350,000 wounded. Those figures couldn’t be independently confirmed and could be an undercount.

Russia resistant to NATO peacekeepers

If peace comes to Ukraine, the number of troops that would help enforce it is vague. Officials have cited figures of between 10,000 and 30,000 troops as part of what's been termed a “reassurance force."

Only Britain and France have said they are willing to send troops, though countries including Australia, Canada, France and Finland say they are open to being involved in some way.

Around 30 leaders were involved in a video meeting on Saturday convened by Starmer.

Russia has said it will not accept any troops from NATO countries being based on Ukrainian soil. And Trump has given no sign the U.S. will guarantee reserve firepower in case of any breaches of a truce. Starmer says the plan won’t work without that U.S. “backstop.”

Jack Watling, a senior research fellow at military think-tank RUSI, said Thursday that the purpose of the Western military force would be to “give Ukraine confidence that a violation of the ceasefire would lead to the Russians having to contend with European forces, and in particular European air power.”

In addition to the meeting in England, EU leaders in Brussels planned to discuss Ukraine’s security needs with Zelenskyy during a meeting about ramping up defense spending after the Trump administration signaled Europe must take care of its own security.

German Chancellor Olaf Scholz said Ukraine must remain an independent democratic nation, continue its journey toward EU membership and maintain strong army after a peace agreement.

The German parliament’s budget committee is expected to decide Friday to clear up to 3 billion euros ($3.3 billion) in extra funding for German military aid to Ukraine this year. That comes after parliament voted to loosen Germany’s debt rules for military and security spending.

Kremlin spokesman Dmitry Peskov said European plans for raising military spending conflicted with Putin and Trump's efforts to reach a peace deal.

“Europe has engaged in militarization and has turned into a party of war,” Peskov said.

Residents of Kyiv interviewed Thursday by The Associated Press voiced a mix of optimism, skepticism and confusion about a potential ceasefire.

Olena Morozova, an accountant, said she hoped Putin would agree to the terms of a peace agreement while Volodymyr Zakusylo, a retiree, said he didn’t trust Trump and he thinks Russia will renege on any agreement.

Natalia Volkotrub, a medic, said she didn’t know what to think because Russia had betrayed Ukraine when it failed to provide the protection it offered when Kyiv agreed to surrender its nuclear weapons after the collapse of the Soviet Union in 1991.

“We gave up our arms and were promised peace and protection,” she said. “But as of today, all promises were broken.”