The US Air Force (USAF) has attacked the Islamic State of Iraq and the Levant (ISIL) with more than 20,000 missiles and bombs since the air strikes began in 2014.
With munitions depleting after 15 months of attacks, the country is planning to replenish its stocks.
Air Force chief of staff Gen. Mark Welsh said Air Force is now "expending munitions faster than we can replenish them."
"B-1s have dropped bombs in record numbers.
"F-15Es are in the fight because they are able to employ a wide range of weapons and do so with great flexibility.
"We need the funding in place to ensure we're prepared for the long fight. This is a critical need," Welsh added.
The USAF is seeking additional funds for Hellfire missiles and plans to increase the production of munitions, but this would take up to four years, an official told CNN.
"The precision today's wars requires demands the right equipment and capability to achieve desired effects.
"We need to ensure the necessary funding is in place to not only execute today's wars, but also tomorrow's challenges." the official added.
As of November, the total cost of operations related to ISIL since operations started on August 8, 2014, is $5.2bn, with the average daily cost being $11.
The US forces damaged or destroyed 16,075 targets including 4,942 fighting positions, more than 4,500 buildings, and 260 oil infrastructures.
Image: A US Marine Corps Hercules aircraft is a part of the Operation Inherent Resolve. US Marine Corps photo by Staff Sgt. Nathan O. Sotelo.