WASHINGTON (AP) — A senior U.S. Treasury official is in Kyiv this week to talk with government officials about U.S. financial support for Ukraine, efforts to tighten sanctions on Russia and plans to use immobilized Russian sovereign assets for the benefit of Ukraine as it fends off Russian forces.

Deputy Secretary Wally Adeyemo's trip comes as Russia gains territory on the battlefield after an especially lengthy delay in U.S. military aid left Ukraine at the mercy of Russia’s bigger army and as the outlook for Ukraine’s state finances is on shakier ground.

Adeyemo is set to meet with officials in Ukraine’s finance ministry and president’s office. He's also planning a stop at the Kyiv School of Economics to speak with faculty and civil society groups working on sanctions policy and ways to make sanctions on Russia more effective.

President Joe Biden signed legislation in April that allows the administration to seize the roughly $5 billion in Russian state assets located in the U.S. However, a majority of the $260 billion in frozen Russian assets are in Europe, and U.S. officials are hoping for a consensus from their European allies on how to spend that money.

U.S. Treasury Secretary Janet Yellen met in Stresa, Italy, with her counterparts from the Group of Seven nations last week to discuss how to squeeze money out of the frozen Russian assets to support Kyiv’s war effort.

She said loaning Ukraine $50 billion from the assets “has been mentioned as a possible number that could be achieved," but that the specific approach was still under discussion.

Since the beginning of Russia’s invasion of Ukraine in February 2022, the U.S. has sanctioned more than 4,000 people and businesses, including 80% of Russia’s banking sector by assets.