The Biden administration on Monday sent Congress an urgent warning about the need to approve tens of billions of dollars in military and economic assistance to Ukraine, saying Kyiv’s war effort to defend itself from Russia’s invasion may grind to a halt without it.

In a letter to House and Senate leaders and also released publicly, Office of Management and Budget Director Shalanda Young warned the U.S. will run out of funding to send weapons and assistance to Ukraine by the end of the year, saying that would “kneecap” Ukraine on the battlefield.

She added that the U.S. already has run out of money that it has used to prop up Ukraine’s economy, and “if Ukraine’s economy collapses, they will not be able to keep fighting, full stop.”