Nearly $6 billion in U.S. funding for aid to Ukraine will expire at the end of the month unless Congress acts to extend the Pentagon's authority to send weapons from its stockpile to Kyiv, according to U.S. officials.

U.S. officials said the Biden administration has asked Congress to include the funding authority in any continuing resolution lawmakers may manage to pass before the end of the fiscal year on Sept. 30 in order to fund the federal government and prevent a shutdown. Officials said they hope to have the authority extended for another year.

They also said the Defense Department is looking into other options if that effort fails.

The officials, who spoke on condition of anonymity to discuss the funding talks, did not provide details on the options. But they said about $5.8 billion in presidential drawdown authority (PDA) will expire. Another $100 million in PDA does not expire at the end of the month, the officials said. The PDA allows the Pentagon to take weapons off the shelves and send them quickly to Ukraine.

They said there is a little more than $4 billion available in longer-term funding through the Ukraine Security Assistance Initiative that will not expire at the end of the month. That money, which expires Sept. 30, 2025, is used to pay for weapons contracts that would not be delivered for a year or more.

Gen. CQ Brown, chairman of the Joint Chiefs of Staff, said Thursday that as the Defense Department comptroller provides options to senior defense and military service leaders, they will look at ways they can tap the PDA and USAI funding.

He said it could be important to Ukraine as it prepares for the winter fight.

"One of the areas that we could do work with them on ... is air defense capabilities and the ability to defend their critical infrastructure," Brown told reporters traveling with him to meetings in Europe. "It's very important to Ukraine on how they defend their national infrastructure, but also set their defenses for the winter so they can slow down any type of Russian advance during the winter months."

Earlier Thursday at the Pentagon, Maj. Gen. Pat Ryder, the press secretary, noted that the PDA gives the Pentagon the ability to spend money from its budget to send military aid to Ukraine. Funding in the $61 billion supplemental bill for Ukraine passed in April can reimburse the department for the weapons it sends.

"Right now, we're continuing to work with Congress to see about getting those authorities extended to enable us to continue to do drawdown packages," said Ryder. "In the meantime, you're going to continue to see drawdown packages. But we'll have much more to provide on that in the near future."

The U.S. has routinely announced new drawdown packages — often two to three a month.

Failure by lawmakers to act on the PDA funding could once again deliver a serious setback in Ukraine's battle against Russia, just five months after a bitterly divided Congress finally overcame a long and devastating gridlock and approved new Ukraine funding.

Delays in passing that $61 billion for Ukraine earlier this year triggered dire battlefield conditions as Ukrainian forces ran low on munitions and Russian forces were able to make gains. Officials have blamed the monthslong deadlocked Congress for Russia's ability to take more territory.

Since funding began again, U.S. weapons have flowed into Ukraine, bolstering the forces and aiding Kyiv's incursion into Russia's Kursk region. Ukraine's forces stormed across the border five weeks ago and put Russian territory under foreign occupation for the first time since World War II.