The Pentagon overstated the amount of U.S. equipment it sent to Ukraine by about $3 billion, a Senate aide and defense official said Thursday, a mistake that opens the door to the possibility that more weapons could be sent to Kyiv to defend against Russian forces. Reuters reports.

The mistake was the result of overvaluing weapons that were taken from U.S. warehouses and then shipped to Ukraine, two senior defense officials said Thursday.

How did the increase in the cost of weapons happen?

“We have found inconsistencies in how we value the equipment that we have provided,” a senior Ukrainian defense official told Reuters. Senate officials and attorneys spoke on condition of anonymity. Congress was notified of the accounting adjustment on Thursday, the sources said.

A Defense Department official said the number of overpriced weapons is likely to rise as the Pentagon takes a closer look at the situation, adding $3 billion.

In accounting, the Pentagon used replacement cost to evaluate weapons aid, rather than the cost of the weapons at the time they were acquired and depreciated, defense officials said.

As of August 2021, the United States has sent approximately $21.1 billion worth of its weapons stockpile to Ukraine.

With the May 9 announcement of a $1.2 billion military aid package, the U.S. has given Ukraine $37.6 billion in military aid since the start of the Biden administration, including $36.9 billion since the war began in February 2022, CNN reported.

The May 9 package included funding for:

• Additional air defense systems and ammunition.
• Equipment for the integration of Western launchers, missiles and radars into the air defense systems of Ukraine.
• Ammunition for unmanned aerial systems
• 155 mm shells
• Services of commercial satellite images
• Training and maintenance support.

Ukrainian Defense Minister Oleksiy Reznikov said at the end of April that the Ukrainian military has almost completed preparations for a counteroffensive against Russian troops. When it begins, it will mark a significant shift in the conflict.

Modern Western tanks, including German Leopard 2 and British Challenger 2, as well as other armored vehicles, such as American Bradley and Stryker, have arrived in Ukraine.