The Democratic and Republican leaders of the US Senate said Tuesday that Washington will not be able to approve new aid for Ukraine before year's end, as the two sides continue to seek a compromise.
"As negotiators work through remaining issues, it is our hope that their efforts will allow the Senate to take swift action... early in the new year," Democrat Chuck Schumer and Republican Mitch McConnell said in a joint statement.
"In the time remaining this year, Senate and Administration negotiators will continue to work in good faith toward finalizing their agreement."
"Challenging issues remain, but we are committed to addressing needs at the southern border and to helping allies and partners confront serious threats in Israel, Ukraine and the Indo-Pacific. The Senate will not let these national security challenges go unanswered."
The announcement from Capitol Hill marked another setback for Ukrainian President Volodymyr Zelensky, whose government has warned of the "dire need" for weapons ahead of winter.
Zelensky flew to Washington in mid-December -- his third trip to the US capital in a year -- to lobby for the aid.
Zelensky remains hopeful, saying at a press conference Tuesday that the United States "will not betray" his besieged nation.
Ukraine's military has failed to mount a major counteroffensive in recent months, and Russian pressure on the frontlines remains stiff.
The congressional impasse is also a blow to President Joe Biden, who has made support for Ukraine and the strengthening of the Atlantic alliance hallmarks of his foreign policy.
Ten months ago, Biden visited Ukraine, the first trip by a US leader to a war-torn country not under US control, underscoring his commitment.
But almost two years after Russian forces invaded Ukraine -- and more than $110 billion in US taxpayer money released by Congress -- questions have come to the fore more insistently about how open-ended the US support is.
Republicans in particular have begun to find the cost too steep. They have made their support for the new package conditional on a drastic tightening of US immigration policy. However, haggling on this hot-button issue did not conclude in time.
To improve prospects for the proposal amid some fatigue over the grinding war, Biden tied his Ukraine request to a proposal to offer $14 billion to Israel, a US ally with broad bipartisan support.
So far, the tactic hasn't pay off.
Since Russian tanks first rolled into Ukraine, the Kremlin has bet that Western military support would ebb. Any hesitation on the part of Kyiv's allies reinforces Russia's belief that its gamble will pay off.
However, the failure of Congress to approve this package does not mean the end of US support for Kyiv.
US lawmakers return to work on January 8, and Republican and Democratic leaders of the Senate have stated their intention to approve the package, which includes military, humanitarian and macro-economic components.
It is in the lower House, which must also approve the aid package, where things get complicated.
New House Speaker Mike Johnson, a Republican, is not opposed in principle to extending US aid, but claims that there is a lack of oversight.
What the Biden administration seems to want are "billions of additional dollars with no appropriate oversight, with no clear strategy to win, and none of the answers that I think the American people are owed," Johnson asserted after his interview with Zelensky on Tuesday.
Johnson, meanwhile, has the hard right of his own party to contend with, including those who don't want to disburse one penny more to Ukraine.
Among them are lawmakers, many close to former president Donald Trump, who were active in the effort to remove the past Speaker in October, accusing him among other things of concluding a "secret deal" on Ukraine with Democrats.
Zelensky voiced awareness of impending risks, saying the return of Trump to the White House could have a "strong impact" on the war in Ukraine.