Ukraine and the United States are in the final stages of negotiating a minerals deal considered central to ending Russia’s three-year-old war in Ukraine, a senior Ukrainian official said on Monday.

Kyiv and Washington are both interested in U.S. access to Ukraine’s undersoil riches, but President Volodymyr Zelenskiy has said any such deal must involve concrete security guarantees.

“Ukrainian and U.S. teams are in the final stages of negotiations regarding the minerals agreement. The negotiations have been very constructive, with nearly all key details finalized,” deputy prime minister Olha Stefanishyna wrote on X.

“We hope both US and UA leaders might sign and endorse it in Washington (at) the soonest to showcase our commitment for decades to come.”

Trump has said Ukraine should give the U.S. $500 billion in critical raw materials as payback for aid which Kyiv has already received from the previous Joe Biden administration.

Zelenskiy said this week Washington had supplied his country with $67 billion in weapons and $31.5 billion in direct budget support, and that he will not acknowledge Biden-supplied aid as loan.

Zelenskiy refused to sign an initial draft deal earlier this month, sparking frustration in the White House. Senior Trump administration officials said on Sunday they expected an agreement would be signed this week.