The Biden administration's national security adviser, Jake Sullivan, was grilled by CNN on Sunday after the Pentagon revealed that the U.S. made at least a $3 billion accounting error in valuing the weapons that it has sent to Ukraine.

"There was this very bizarre admission from the Pentagon this week of an accounting error that suggested that the U.S. has at least $3 billion that it didn’t know it had that it can use for Ukraine aid," CNN anchor Jake Tapper said.

"That’s a hell of an accounting error. And it provides a lot of fodder to critics of U.S. aid to Ukraine and critics who say there’s not enough oversight going on. Are you concerned about this accounting error?" Tapper asked Sullivan.

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Jake Tapper and Jake Sullivan

National Security Advisor Jake Sullivan was grilled by CNN Sunday after the Pentagon revealed that the U.S. made at least a $3 billion accounting error in valuing the weapons that it has sent to Ukraine. (CNN / Screenshot)

The Pentagon admitted Thursday that it overestimated the value of weapons it has sent to Ukraine by $3 billion – the admission comes amid ongoing criticism from some GOP members of Congress that American funding for the war in Ukraine threatens further escalation of the conflict, according to AP News. Sullivan, however, argued that the $3 billion was a fortunate accounting mistake that will allow even more funding for weapons to Ukraine.

Deputy Defense Press Secretary Sabrina Singh told Fox News Digital in a statement that "the Department discovered inconsistencies in equipment valuation for Ukraine" during its "oversight process of presidential drawdown packages."

"In some cases, ‘replacement cost’ rather than ‘net book value’ was used, therefore overestimating the value of the equipment drawn down from U.S. stocks. This over-valuation has not constrained our support to Ukraine nor impacted our ability to flow capabilities to the battlefield," Singh said.

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Pentagon spokeswoman Sabrina Sengh

Deputy Defense Press Secretary Sabrina Singh told Fox News Digital in a statement that "the Department discovered inconsistencies in equipment valuation for Ukraine" during its "oversight process of presidential drawdown packages." (Kevin Dietsch/Getty Images)

A defense official also told Fox News Digital that the Department of Defense will not constrain the government's "support to Ukraine."

"That is not money that went out the door and disappeared," Sullivan told Tapper.

"That is not a waste of that $3 billion. It is simply a tally of how much military equipment we have given them. And the way that the Pentagon was counting it was what’s the replacement cost for the equipment we provide rather than just the actual cost of that equipment. Once you make that adjustment, it turns out we have an additional $3 billion that we can spend to provide even more weapons to Ukraine," he said.

"At the end of the day, not one penny of U.S. dollars will have gone missing or have been misallocated," Sullivan said. 

An aerial photo of the Pentagon

The Pentagon (Staff/AFP via Getty Images)

Sullivan conceded that it would have been better if the Pentagon got it right "in terms of the accounting up front" but said that the American taxpayer can be "confident that this money is being spent effectively and appropriately" and that Ukraine will "get what it needs."

The U.S. government has provided nearly $40 billion in military aid since Russia invaded in late February 2022. Nineteen House and Senate Republican lawmakers sent a letter to President Joe Biden last Thursday, calling for the administration to stop sending U.S. aid to Ukraine and arguing that tension with Russia has only escalated with every additional aid package that the United States sends.

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Fox News' Bradford Betz and Haley Chi-Sing contributed to this report.