WASHINGTON (Reuters) - U.S. President Donald Trump said on Monday he wants Ukraine to supply the United States with rare earth minerals as a form of payment for financially supporting the country's war efforts against Russia.

Trump, speaking to reporters at the White House, said Ukraine was willing, adding that he wants "equalization" from Ukraine for Washington's "close to $300 billion" in support.

"We're telling Ukraine they have very valuable rare earths," Trump said. "We're looking to do a deal with Ukraine where they're going to secure what we're giving them with their rare earths and other things."

It was not immediately clear if Trump was using the term "rare earths" to refer to all types of critical minerals or just to rare earths.

Rare earths are a group of 17 metals used to make magnets that turn power into motion for electric vehicles, cellphones and other electronics. There are no known substitutes.

The U.S. Geological Survey considers 50 minerals to be critical for the country's economy and national defense, including several types of rare earths, nickel and lithium.

Ukraine contains large deposits of uranium, lithium and titanium, although none are considered to be among the world's five biggest by volume and the U.S. has its own untapped reserves of those and other critical minerals.

The U.S. has only one operating rare earths mine and very little processing capacity, although several companies are working to develop projects in the country. China is the world's largest producer of rare earths and many other critical minerals.