(Bloomberg) -- President Joe Biden’s budget director warned Monday that the US would run completely out of resources to assist Ukraine by the end of the calendar year, as the White House looks to ratchet up pressure on lawmakers to pass an emergency funding package.

“There is no magical pot of funding available to meet this moment,” Shalanda Young, who leads the Office of Management and Budget, wrote in a letter to congressional leaders. “We are out of money — and nearly out of time.”

A failure to act, Young warned, would “kneecap Ukraine on the battlefield, not only putting at risk the gains Ukraine has made, but increasing the likelihood of Russian military victories.”

Ukraine assistance has become a flashpoint on Capitol Hill, with new House Speaker Mike Johnson insisting that additional aid is contingent on immigration policy changes. 

Johnson said Monday that the Biden administration had failed to address House Republicans’ “legitimate concerns about the lack of a clear strategy in Ukraine, a path to resolving the conflict, or a plan for adequately ensuring accountability for aid provided by American taxpayers.”

In a post on X, the platform formerly known as Twitter, Johnson said any additional national security funding “must begin with our own border.”

“We believe both issues can be agreed upon if Senate Democrats and the White House will negotiate reasonably,” he added.

The White House is seeking over $61 billion for Ukraine aid as part of a roughly $105 billion package that would also include funding for Israel’s war against Hamas, US allies in the Pacific and money to house and process undocumented immigrants along the border with Mexico.

Read more: Senate Border Policy Talks Drag, Jeopardizing US Aid to Ukraine

Republicans are hoping the Ukraine funding fight can provide leverage as they seek to tighten access to asylum for those entering the US. But negotiations on a sweeping immigration agreement are yet to yield results, with the Senate expected to depart for the Christmas holiday on Dec. 15.

“It’s going to take the administration coming to the table and recognizing that their policy needs to change,” House Intelligence Committee Chairman Mike Turner, an Ohio Republican, said Sunday on CBS News’s “Face the Nation.” “America overwhelmingly wants the southern border addressed. It represents a national security threat.”

Senator James Lankford, an Oklahoma Republican involved in the negotiations, said Sunday he still believed it was possible to get a deal on immigration and foreign aid “done by the end of the year.”

“People want a legal, orderly process, not the chaos that we currently have on our southern border — that shouldn’t be too tall of an order to be able to fulfill,” Lankford said in an interview on ABC News’s “This Week.”

Read more: GOP Negotiator Sees US Border Policy Deal Possible by Year’s End

But the push is further complicated by other pressing business on Capitol Hill, including reauthorization of legislation allowing the warrantless collection of communications of non-Americans, as well as the annual defense authorization legislation. And the White House is eager to settle the funding issue before January, when it could bleed into the latest round of fighting over government funding.

In the interim, both Ukraine and the Biden Administration are looking to publicly highlight the impact of a funding lapse. 

Ukrainian President Volodymyr Zelenskiy said his country’s counteroffensive did not achieve its desired goals because allies had not provided hoped-for weapons.

“In the case of Ukraine, if resilience fails today due to lack of aid and shortages of weapons and funding, it will mean that Russia will most likely invade NATO countries,” Zelenskiy said in an interview this week with the Associated Press. “And then the American children will fight.”

The White House also argued that the funding would help boost the US industrial base, because old weapons systems would be shipped to Ukraine and replaced by new items built in the United States. Budget director Young estimated that nearly half of the president’s emergency request would be funneled into manufacturing in the US.

“While we cannot predict exactly which US companies will be awarded new contracts, we do know the funding will be used to acquire advanced capabilities to defend against attacks on civilians in Israel and Ukraine — for example, air defense systems built in Alabama, Texas, and Georgia, and vital subcomponents sourced from nearly all 50 states,” Young said. 

The administration is expected to further brief lawmakers this week on the consequences of not renewing the funding by the end of the year.

--With assistance from Erik Wasson.

(Adds Johnson comment starting in fifth paragraph)

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