Russell Vought, director of the White House Office of Management and Budget, declined to give senators an estimate of the cost of the military operations against Iran when pressed on the issue during a hearing Thursday.

Vought said the White House is working on a request for additional defense funding but declined to offer an estimate of how much the war has cost taxpayers so far, telling lawmakers that the costs “fluctuate” day to day.

Asked by Sen. Jeff Merkley (D-Ore.) if the administration has already spent $50 billion on the conflict, as some media reports have indicated, Vought said: “I wouldn’t [want] to make a characterization of that at this point.”