KYIV, Ukraine — Senior military officers from countries across Europe and beyond will meet Thursday outside London 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 the “coalition of the willing” plan, led by Britain and France, is moving into an “operational phase.” But it’s unclear how many countries are willing to send troops, or whether there will be any ceasefire to protect.

Ukraine and Russia agreed in principle Wednesday to a limited ceasefire after 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.

The tentative deal to partially rein in the three-year war came after Russian President Vladimir 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 to 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.

Related Story: Zelenskyy Disputes Putin’s Vow Not to Hit Ukraine’s Energy Infrastructure

No Break in Fighting as Casualties Mount

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.

The U.K. Defense Ministry estimated that 900,000 Russian troops have been killed or wounded since Moscow’s invasion of Ukraine three years ago. That’s a jump of 200,000 from its estimate in the fall after it said Russian forces suffered heavy losses in October.

Defense intelligence said up to 250,000 Russian soldiers had been killed.

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.

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

Related Story: Putin and Trump Will Speak on Tuesday About the War in Ukraine

Russia Resistant to NATO Peacekeeping Force

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.

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.

“This is more than just a focus on troops. We’re talking about protection in air, at sea, and all the operational planning that is needed,” Starmer’s spokesman Dave Pares said. “What one country can contribute will be different to other countries.”

Around 30 leaders were involved in a video meeting on Saturday including Macron, Zelenskyy, Italian Prime Minister Giorgia Meloni, leaders from Australia, Canada and New Zealand and officials from NATO and the European Union.

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.”

European Leaders Discuss Ukraine’s Security Needs

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 it’s “central” that Ukraine must remain an independent democratic nation, that it can continue its journey toward EU membership and “that it also has a strong army of its own 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.

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Follow the AP’s coverage of the war at https://apnews.com/hub/russia-ukraine