Ukraine's allies say they have agreed to provide the country with multi-layered international defence guarantees as part of a proposal to end Russia's nearly four-year-old invasion of its neighbour.
At a key meeting in Paris on Tuesday, local time, leaders from European countries and Canada, as well as US representatives and top officials from the European Union and NATO, said they would provide Kyiv's frontline forces with equipment and training, and back them up with air, land and sea support to deter any future Russian attack.
The size of the supporting forces was not made public, and many of the plan's details remain unclear.
Ukrainian President Volodymyr Zelenskyy, writing on Telegram after the meeting, said the agreements were "a signal of how seriously Europe and the entire coalition of the willing are ready to work for real security".
But he added that it remained to be determined how the monitoring would work and how the Ukrainian army would be supported and financed.
Mr Zelenskyy thanked the United States "for its readiness to be a backstop in all areas — security guarantees, monitoring a ceasefire and rebuilding", and said the Ukrainian delegation would continue its talks on key issues.
UK Prime Minister Sir Keir Starmer said those at the meeting had made "excellent progress", but cautioned that "the hardest yards are still ahead", noting that Russian attacks on Ukraine continue.
He said allies would participate in US-led monitoring and verification of any ceasefire, support the long-term provision of armaments for Ukraine's defence, and work toward making their commitment to support Ukraine in the case of any future attack by Russia legally binding.
There was no immediate comment from officials in Russia on Tuesday, which was the eve of Orthodox Christmas.
Moscow has revealed few details of its stance on security guarantees in the US-led peace negotiations.
Officials have reaffirmed Russia's demands and have insisted there can be no ceasefire until a comprehensive settlement is agreed, and Russian President Vladimir Putin has ruled out agreeing to any deployment of troops from NATO countries on Ukrainian soil.
Sir Keir said there could only be peace if Russia compromises, and "Putin is not showing that he is ready for peace".
In the event of a ceasefire, he said the UK and France would "establish military hubs across Ukraine and build protected facilities for weapons and military equipment to support Ukraine's defensive needs".
A joint statement said the allies also agreed to continue long-term military assistance and armament to Ukraine's armed forces, which "will remain the first line of defence and deterrence" after any peace deal is signed.
French President Emmanuel Macron said the statement was a "significant step" toward ending Russia's invasion.
Mr Zelenskyy acknowledged the progress that had been made in the talks, although he reiterated that commitments needed to be ratified by each country so that they could be put in place after any settlement.
"We determined what countries are ready to take leadership in the elements of security guarantees on the ground, in the air, and at sea, and in restoration," Mr Zelenskyy told a news conference in Paris.
"We determined what forces are needed. We determined how these forces will be operated, and at what levels of command."
US envoy Witkoff says Trump backs security guarantees
Prospects for progress at the meeting had been viewed as uncertain, as the Trump administration's focus has shifted to Venezuela, while US suggestions of a Greenland takeover are causing tension with Europe, and Moscow is showing few signs of compromise.
The countries dubbed the "coalition of the willing" have been exploring for months how to deter any future Russian aggression should it agree to stop fighting Ukraine.
Mr Macron's office said an unprecedented number of officials had attended the meeting in person, with 35 participants, including 27 heads of state and government.
Mr Trump's Ukraine envoy, Steve Witkoff, and Mr Trump's son-in-law, Jared Kushner, also met with Mr Macron at the Elysee presidential palace for preparatory talks ahead of the gathering.
The US delegation was initially set to be led by Secretary of State Marco Rubio, but he changed his plans after the US military intervention in Venezuela.
Support from nuclear-armed powers 'essential'
Speaking over the weekend, Mr Zelenskyy noted that "not everyone is ready" to deploy forces in Ukraine to enforce a peace deal, but said he recognised that support could come in forms other than troops, such as weapons, technology and intelligence.
However, Mr Zelenskyy said troop deployments by Britain and France, Western Europe's only nuclear-armed nations, would be "essential".
"Speaking frankly as president, even the very existence of the coalition depends on whether certain countries are ready to step up their presence," he said.
"If they are not ready at all, then it is not really a 'coalition of the willing.'"
Also on Tuesday, Ukraine's Security Service (SBU) carried out drone strikes on a military arsenal and an oil depot deep inside Russia, according to a security official who was not authorised to comment publicly and thus spoke on condition of anonymity.
The long-range drones hit the arsenal in Russia's Kostroma region, triggering explosions that lasted for hours and forced the evacuation of nearby settlements, the official said.
The site was described as a key logistics hub supplying ammunition in western and central Russia.
In a separate strike, SBU drones hit an oil depot in Russia's Lipetsk region, causing a huge fire, the official said.
AP, Reuters, ABC