The Pentagon is warning Congress that it is running out of money to replace weapons the U.S. sent to Ukraine and has already been forced to delay supplies to some troops, according to a letter to congressional leaders.

The letter, obtained by the Associated Press, urges Congress to supplement funding for Ukraine. Congress averted a government shutdown by passing a short-term funding bill this weekend, but the measure cut all aid to Ukraine in its fight against Russia.

Pentagon Comptroller Michael McCord told House and Senate leaders that $1.6 billion remains of the $25.9 billion Congress has appropriated to replenish U.S. military supplies that have flowed into Ukraine. The weapons include millions of artillery rounds, missiles and rockets that are crucial to Ukraine’s counteroffensive aimed at taking back territory Russia captured in the war.

In addition, the US still has approximately $5.4 billion left to supply weapons and equipment from its stockpiles. The U.S. would already have run out of that funding if the Pentagon hadn’t realized earlier this year that it had overvalued the equipment it had already sent, freeing up about $6.2 billion. Some of that has been shipped in recent months.

McCord said the U.S. has run out of long-term funding for Kiev through the Ukraine Security Assistance Initiative, which provides money for future weapons contracts.

We have already been forced to delay the replenishment of our own forces to hedge against an uncertain funding future, McCord said in the letter. Failure to replenish our military services in a timely manner could harm the readiness of our military.

He added that without additional funding now, the US will have to delay or limit air defense weapons, munitions, drones and demolition and breaching equipment that are now critical and urgent as Russia prepares for a winter offensive.

President

Joe

Biden said Sunday that while aid will continue to flow for now, time is running out.

We cannot, under any circumstances, allow US support to Ukraine to be interrupted, Biden said. We have time, not a lot of time, and there is an overwhelming sense of urgency.

Mark Cancian, a senior

counselor

of the Center for Strategic and International Studies said that if aid does not continue to flow, Ukrainian resistance will begin to weaken.

If there is no new money, they will start on Thanksgiving, he said.

The short-term funding bill passed by Congress only lasts until mid-November. And McCord said it would be too risky for the Defense Department to take money from that temporary funding bill to pay for more aid to Ukraine.

Much of the legislation recognizes that it will become more difficult to gain approval for Ukraine aid in Congress as the war rages on and opposition to aid from the Republican far-right flank gains momentum.