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.

Just last week, Trump described Zelensky as a “dictator”, and appeared to blame Ukraine – not Russia – for starting the war, after the Ukrainian leader rejected US demands for $500bn in mineral wealth and suggested that the American president was living in a “disinformation space” created by Russia.

Trump has been pushing for access to Ukraine’s minerals in return for previous military and other aid to the country since Moscow launched a full-scale invasion three years ago.

Zelensky argued nowhere near that much American aid had been provided, adding: “I can’t sell our state.”

On Tuesday, Trump said the US had given Ukraine between $300bn and $350bn.

“We want to get that money back,” he told reporters. “We’re helping the country through a very very big problem… but the American taxpayer now is going to get their money back plus.”

Ukraine’s Deputy Prime Minister Olha Stefanishyna told the Financial Times – which first reported the minerals deal on Tuesday – that the deal was “only part of the picture”.

“We have heard multiple times from the US administration that it’s part of a bigger picture,” said Stefanishyna, who has led the negotiations.

According to Ukrainian sources, the US has had to back away from some of its more onerous demands from the war-torn nation and many of the details of this agreement will require further negotiation.

The precedent, however, is set. US aid in the Trump era comes with strings attached. Aid for aid’s sake – whether given for humanitarian or strategic reasons – is a thing of the past.

That represents a fundamental reordering of American foreign policy for more than 75 years, from the days of the Marshall Plan to post-Cold War idealism and George W Bush’s “Freedom Agenda” push to promote global democracy.

Ukraine is just the start. Expect Trump and his foreign policy team to apply their “America First” principles around the world over the course of the next four years.

Ukraine’s news site Ukrainska Pravda reported that the minerals deal was set to be signed by Ukrainian Foreign Minister Andrii Sybiha and US Secretary of State Marco Rubio.

The news site’s economics unit EP said the two countries had also agreed to set up a reconstruction investment fund.

Ukraine holds huge 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.

Last year, Zelensky presented a “victory plan” to Ukraine and its Western partners which proposed that foreign firms could gain access to some of the countries’ mineral wealth at the end of the war.

On Tuesday, Russian President Vladimir Putin said he was open to offering the US access to rare minerals, including from Russian-occupied regions of Ukraine.

Ukraine and its European allies have become increasingly alarmed over a recent thaw in US-Russian ties, including their bilateral talks in Saudi Arabia last week.

There is concern in Kyiv and across Europe that they might be excluded from any negotiations aimed at ending the war, and that the continent’s future security as a whole could be decided behind their backs.

It is estimated that about 5% of the world’s “critical raw materials” are in Ukraine – including:

• 19 million tonnes of proven reserves of graphite, which is used to make batteries for electric vehicles

• A third of all European lithium deposits, the key component in current batteries.

Before Russia’s full-scale invasion began three years ago, Ukraine also produced 7% of the world’s titanium, used in construction for everything from aeroplanes to power stations.

Ukrainian land also contains significant deposits of 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

Some mineral deposits have been seized by Russia. According to Yulia Svyrydenko, Ukraine’s economy minister, resources worth $350bn remain in Russian-occupied territories today.