When US President Donald Trump told Volodymyr Zelenskyy he "had no cards" during an awkward Oval Office meeting last month, he might have forgotten the very reason his Ukrainian counterpart was there.
Mr Zelenskyy had travelled to Washington to sign a critical minerals deal.
The arrangement would give the US a future 50 per cent stake in Ukraine's vast, state-owned mineral wealth as well as oil and gas reserves, in exchange for the military and financial aid Washington has been giving Kyiv since Russia's full-scale invasion three years ago.
But since the deal signing turned into a dressing down and Mr Zelenskyy was told to leave the White House, the agreement has been in limbo.
After a meeting between delegations from Ukraine and the US in Saudi Arabia this week, both leaders agreed to get something signed "as soon as possible".
So, what lies beneath the ground in Ukraine? And why does Mr Trump want it?
What lies beneath
Ukraine claims it has deposits of 22 of the 34 minerals identified by the European Union (EU) as critical, including industrial and construction materials, ferroalloy, and precious and non-ferrous metals.
There is lithium and graphite, which are essential for making batteries, iron for making steel, manganese for batteries and steel, and titanium and zinc, which are used in everything from aeroplanes to power stations, to name a few.
There has also been a lot of discussion about the presence of rare earths, which are found in the components of many devices we use in our modern lives, but geologists the ABC has spoken to are doubtful there are vast deposits.
Professor Pierre Josso, deputy director of the UK Critical Minerals Intelligence Centre at the British Geological Survey, said rare earth elements in Ukraine were not well known, and "poorly characterised, if present at all".
"Effectively there isn't a lot of data about potential deposits of rare earths in Ukraine," Professor Josso said.
"Ukraine is not necessarily the place, with the current state of play and knowledge from most geologists around the world, where one would definitely think, 'oh, I'm going to go to Ukraine to explore for big rare earth deposits', that's not really the case.
"There are, however a lot of other metals, which are equally important for the type of technologies that are used in aerospace and defence, as well as strategic commodities for decarbonisation, for electric vehicles, for energy security and digital transformation."
And that's likely why Mr Trump is so interested.
The China factor
Mr Trump's aims appear to be twofold; to recoup Washington's financial and military support for Ukraine since Russia's invasion, and limit America's reliance on Chinese resources.
"The whole discussion context around critical metals or strategic metals and material is really a geopolitical one [and] currently, the main issue for Western nations is their dependence on China," Professor Josso said.
"China completely concentrates the refining stage of most of the materials which are used for the development of new technologies, and effectively this dependency is a security threat, potentially, that can be used as a levy against other nations."
Geologist Adrian Finch from St Andrews University in Scotland told the ABC the United States was smart to be looking at diversifying where they get their natural resources from.
"I think that any wise government should be doing precisely that," Professor Finch said.
"Perhaps we might disagree with the style in which it's being done [by Donald Trump], but certainly, I think that this is part of a genuine attempt to ensure that there is security for the US in access to natural resources."
And that, he added, is essential as nations try to offset emissions.
"I think that the world is putting together net zero aspirations without really thinking very much about where those resources are coming from," Professor Finch said.
"And if you don't put into a plan and into practice some form of strategy to bring resources to the market … then all of these net zero statements and aspirations simply become hot air."
Difficult to access
Kyiv says its resources represent trillions of dollars of untapped mineral wealth, but Professors Josso and Professor Finch said they thought it would take years for investors to make significant profits from the Ukrainian mining industry — a sector reeling from war and chronic underinvestment.
Even without a war around you, mining is a long game.
"The time lag between deciding you wish to exploit a natural resource and then being in a position to put it into the market in a reasonable volume is certainly years, and in many cases, is decades," Professor Finch said.
And then there is the question of how much of its resources Ukraine still has access to.
The war has caused widespread damage, and Russia now controls about a fifth of Ukraine's territory.
The bulk of its coal deposits, which powered its steel industry before the war, are concentrated in the east and have been lost.
Ukrainian think-tanks We Build Ukraine and the National Institute of Strategic Studies claim about 40 per cent of Ukraine's metal resources are now under Russian occupation, citing data up to the first half of 2024.
Since then, Russian troops have continued to advance steadily in the eastern Donetsk region.
In January, Ukraine closed the only remaining working coal mine it controlled, outside the city of Pokrovsk, as Moscow's forces closed in.
Russia has occupied at least two Ukrainian lithium deposits during the war — one in Donetsk and another in the Zaporizhzhia region in the south-east.
Ukraine's end of the deal
So if the US and Ukraine do sign a minerals deal, and the US recoups millions of dollars and competes with China on minerals, what does Ukraine get?
The statement from the Saudi Arabia talks between officials from Washington and Kyiv said the deal would help Ukraine too, by developing the country's critical mineral resources, which would in turn expand the economy, but there were no further details.
The statement, or at least the one made publicly, did not include what Kyiv really wants: explicit security guarantees.
Australian mining billionaire, Andrew Forrest, a vocal supporter of Ukraine who's donated millions of dollars to the country since Russia's full-scale invasion, told the ABC he believed the US, and other nations, must stand up for Ukraine.
"My thought on the minerals deal — as someone who stands rock-solid behind the people of Ukraine, rock-solid behind President Zelenskyy and rock-solid behind the very sovereignty of Ukraine — is that this could be a good deal. It isn't yet," Mr Forrest said.
"Right now, President Zelenskyy has done what the Trump administration has asked and offered up a great deal of resources of Ukraine to the United States in return for a question mark, and that question mark must be answered.
"Look, this could be a good deal. Provided that it leads to the freedom and sovereignty of Ukraine."
