US President Joe Biden and Pentagon chief Lloyd Austin. Photo: EPA

The Pentagon has warned Congress that it is running low on money to replace weapons the US has sent to Ukraine and urged American lawmakers to replenish funding for Kyiv, in a letter obtained by The Associated Press news agency.

The letter, sent by Pentagon comptroller Michael McCord to the leaders of the House and the Senate, came as the lawmakers averted a US government shutdown by passing a temporary, 45-day budget resolution excluding additional funding for Ukraine aid.

Mr McCord told House and Senate leaders there is USD 1.6 billion left of the USD 25.9 billion Congress provided to replenish US military stocks that have been flowing to Ukraine. Those include millions of rounds of artillery, rockets and missiles critical to Ukraine’s counteroffensive aimed at taking back territory gained by Russia in the war.

In addition, the US has about USD 5.4 billion left to provide weapons and equipment from its stockpiles.

The Pentagon official said the US has completely run out of long-term funding for Kyiv through the Ukraine Security Assistance Initiative, which provides money to contract for future weapons.

"We have already been forced to slow down the replenishment of our own forces to hedge against an uncertain funding future," Mr McCord said in the letter. "Failure to replenish our military services on a timely basis could harm our military’s readiness."

He added that without additional funding now, the US will have to delay or curtail air defence weapons, ammunition, drones and demolition and breaching equipment that are "critical and urgent now as Russia prepares to conduct a winter offensive."

The White House had asked Congress to provide USD 24 billion for Ukraine through the end of 2023, but a right-wing group of the Republicans in the House has opposed any additional aid for Kyiv as it fends off Russia’s full-scale aggression.

US president Joe Biden said on Sunday that while the aid will keep flowing for now, time is running out.