The Pentagon made an accounting mistake by overestimating the value of the U.S. equipment dispatched to Ukraine by approximately $3 billion, a Senate aide and a defense official said, an error that creates an opportunity for the provision of additional weapons to Kyiv in order to bolster its defense against Russian forces.

The error was the result of assigning a higher than warranted value on weaponry that was taken from U.S. stocks and then shipped to Ukraine, two senior defense officials said on Thursday.

"We've discovered inconsistencies in how we value the equipment that we've given," to Ukraine one of the senior defense officials told Reuters.

The officials and the Senate aide spoke on the condition of anonymity. Congress is being notified of the accounting adjustment on Thursday, the sources said.

The defense official said it is possible the amount of overvalued weaponry could grow as the Pentagon examines the situation more thoroughly, increasing the $3 billion.