Reuters
Ukraine's President Zelensky first discussed a minerals deal with then presidential candidate Donald Trump last September.
Ukraine has agreed to the terms of a major deal giving the US access to its deposits of rare earth minerals, Volodymyr Zelensky has said.
Kyiv hopes the deal – which would give the US a financial stake in the country – will encourage the White House to protect Ukraine if the war with Russia reignites after a potential ceasefire.
US President Donald Trump said an agreement would help American taxpayers "get their money back" for aid sent to Ukraine throughout the war and would give Ukraine "the right to fight on" against Russia.
But Ukrainian President Zelensky said no US security guarantees had been agreed yet, but he hoped the agreement would "lead to further deals".
What are the terms of the deal?
Key details have not yet been made public, but on Wednesday Ukrainian Prime Minister Denys Shmyhal said Ukraine and the US had finalised a version of the agreement.
Speaking to Ukrainian TV, Shmyhal said the preliminary agreement envisages that an "investment fund" will be set up for Ukraine's reconstruction.
Kyiv and Washington will be managing the fund on "equal terms", the prime minister added.
He said Ukraine would contribute 50% of future proceeds from state-owned mineral resources, oil and gas to the fund, and the fund would then invest in projects in Ukraine itself.
The New York Times reported, citing a draft document, that the US would own the maximum amount of the fund allowed under US law, but not necessarily all of it.
A minerals deal was at the centre of a rift between Trump and Zelensky last week, with the Ukrainian president rejecting an initial request for $500bn (£395bn) in revenue from rare minerals.
Media reports say this demand has since been dropped.
"The provisions of the deal are much better for Ukraine now," a source in Ukraine's government told the BBC.
On Tuesday, Trump said the US had given Ukraine between $300bn (£237bn) and $350bn (£276bn) in aid, and that he wanted to "get that money back" through a deal.
BBC Verify analysis did not find evidence for this figure.
Does the deal include a security guarantee?
Zelensky has been pushing for a deal to include a firm security guarantee from the US.
But on Wednesday, Ukraine's leader said no such guarantee had been made.
"I wanted to have a sentence on security guarantees for Ukraine, and it's important that it's there," he said.
Asked by the BBC if he would be prepared to walk away from the agreement if Trump did not offer the guarantees he wanted, Zelensky said: "I want to find a Nato path or something similar.
"If we don't get security guarantees, we won't have a ceasefire, nothing will work, nothing."
Despite this, Ukrainian PM Shmyhal said on Wednesday the US supported "Ukraine's efforts to obtain security guarantees to build lasting peace".
He said Ukraine would not sign the deal until Zelensky and Trump "agree on security guarantees" and decide on how to "tie this preliminary agreement" to a US security guarantee.
Yuri Sak, adviser to Ukraine's ministry of strategic industries, told the BBC earlier on Wednesday: "There's no point in signing any deal on critical minerals if Russians can reinvade one month after signing the deal."
He said discussions about security guarantees needed to continue.
Meanwhile, Deputy Prime Minister Olha Stefanishyna, who has been leading negotiations, told the Financial Times that the deal was "part of a bigger picture".
The prospect of a minerals deal was first proposed by Zelensky last year as a way to offer the US a tangible reason to continue supporting Ukraine.
Trump said on Tuesday that Ukraine would get "the right to fight on" in return for access to its minerals, though he did not confirm an agreement had yet been reached.
He suggested the US would continue to supply equipment and ammunition to Ukraine "until we have a deal with Russia".
He also said there would be a need for "some form of peacekeeping" in Ukraine following any peace deal, in a form that would need to be "acceptable to everyone".
When will the deal be signed?
Shmyhal said the US and Ukraine have prepared a final version of the agreement, which Ukraine's government will authorise for signing on Wednesday.
Trump has said he expects Zelensky to sign the deal on a visit to Washington on Friday.
Zelensky said he would be "very direct" with Trump by asking whether the US would continue supporting Ukraine or not.
What minerals does Ukraine have?
Kyiv estimates that about 5% of the world's "critical raw materials" are in Ukraine.
This includes some 19m tonnes of proven reserves of graphite, which the Ukrainian Geological Survey state agency says makes the nation "one of the top five leading countries" for the supply of the mineral. Graphite is used to make batteries for electric vehicles.
Ukraine also has significant deposits of titanium, lithium and rare earth metals - a group of 17 elements that are used to produce weapons, wind turbines, electronics and other products vital in the modern world.
How has Russia reacted?
Vladimir Putin has not yet addressed reports that the terms of a deal between the US and Ukraine have been agreed.
But on Monday evening he told state TV he was ready to "offer" resources to American partners in joint projects, including mining in Russia's "new territories" - a reference to parts of eastern Ukraine that Russia has occupied since launching a full-scale invasion three years ago.
Putin said a potential US-Ukraine deal on rare minerals was not a concern and that Russia "undoubtedly have, I want to emphasise, significantly more resources of this kind than Ukraine".
"As for the new territories, it's the same. We are ready to attract foreign partners to the so-called new, to our historical territories, which have returned to the Russian Federation," he added.