The Biden administration made an accounting error in assessing the value of the military support that the US has given to Ukraine to date, freeing up approximately $3 billion more in aid, an amount likely to mitigate the need for Congress to pass an additional assistance package before the end of the fiscal year in September, multiple congressional and administration officials told CNN.

The error -- which lawmakers and congressional staffers were briefed on Thursday -- triggered frustration from Republicans on the House Foreign Affairs and Armed Services committees. They believe the mistake reduced the amount of US support that went to Ukraine leading up to the counteroffensive.

"The revelation of a three-billion-dollar accounting error discovered two months ago and only today shared with Congress is extremely problematic, to say the least. These funds could have been used for extra supplies and weapons for the upcoming counteroffensive, instead of rationing funds to last for the remainder of the fiscal year," wrote House Foreign Affairs Chairman Michael McCaul and House Armed Services Chairman Mike Rogers in a statement Thursday.

Before this new information came to light the Pentagon had said that there was just over $2.3 billion remaining available for Presidential Drawdown Authority for Ukraine. Now, due to this revelation, there is about $5.3 billion still available, far more than even the largest single package provided to Ukraine.

The briefing to the Hill comes after the White House told CNN that it is not currently planning to ask Congress for new Ukraine funding before the end of the fiscal year at the end of September, which pit administration officials against some lawmakers and congressional staffers who are concerned that the funds could run out by mid-summer.

But now that there is more funding available, congressional sources said they are less concerned about the immediate need for a new funding package for Ukraine. They believe it is likely that the newfound funding will carry the US support to Ukraine through the end of the summer.

The accounting error occurred because when the US transferred weaponry to Ukraine, they counted the value of replacing the weapon instead of the value of actual weapon, defense officials explained. That drove up the cost of each package -- because new weaponry costs more than old weaponry -- and resulted in the false assumption that more of the funding had been used.

McCaul and Rogers said that the administration should "make up for this precious lost time by using these funds to provide Ukraine the DPICMS and ATACMS they need to fuel the counteroffensive and win the war."

The US has resisted providing Ukraine with Army Tactical Missile Systems -- which can reach targets over 185 miles away -- both because the missiles are in limited supply and because the US is worried Russia would see them as too provocative. The US has also resisted sending cluster munitions to Ukraine -- known as dual-purpose improved conventional munitions or DPICMs -- because many countries are ardently opposed to it and the US believes there are too many downsides to the use of cluster munitions due to the high risk they pose to civilians.