Ukraine has agreed the terms of a major minerals deal with the US, a senior official in Kyiv has told the
BBC.
"We have indeed agreed it with a number of good amendments and see it as a positive outcome," the official said, without providing any further details.
Media reports say Washington has dropped initial demands for a right to $500bn (£395bn) in potential revenue from utilising the natural resources but has not given firm security guarantees to war-torn Ukraine - a key Ukrainian demand.
US President Donald Trump said he was expecting his Ukrainian counterpart Volodymyr Zelensky in Washington to sign the deal this week, after the two leaders exchanged strong words about each other.
Without confirming that an agreement had been reached, Trump said on Tuesday that in return for the deal Ukraine would get "the right to fight on".
"They're very brave," he told reporters, but "without the United States and its money and its military equipment, this war would have been over in a very short period of time".
Asked whether supplies of US equipment and ammunition to Ukraine would continue, he said: "Maybe until we have a deal with Russia... We need to have a deal, otherwise it's going to continue."
There would be a need for "some form of peacekeeping" in Ukraine following any peace deal, Trump added, but that would need to be "acceptable to everyone".
Ukraine holds deposits of critical elements and minerals, including lithium and titanium, as well as sizeable coal, gas, oil and uranium deposits - supplies worth billions of dollars.
Trump claims this deal would see the US receive more than it had spent on Ukraine, but more details reportedly need to be ironed out.
According to a source in Ukraine's presidential office, what has been agreed at this stage are the initial terms of an agreement that includes the country's critical minerals and other resources.
"The provisions of the deal are much better for Ukraine now," they added.
Reports suggest it would see the creating of a jointly owned fund, which would be used to rebuild Ukraine's infrastructure and economy. 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.
Ukraine's Deputy Prime Minister Olha Stefanishyna, who has been leading negotiations, told the Financial Times that the deal was "part of a bigger picture".
