The 2015 US defense funding bill would prohibit the future purchase of Russian-made rocket engines, used to launch US national security satellites, but will honor existing contracts and provide for national security exemptions, the draft document says.

According to the 2015 National Defense Authorization Act, the US Secretary of Defense may issue a waiver if a "contract could not be obtained at a fair and reasonable price without the use of rocket engines, designed or manufactured in the Russian Federation", even though under the new regulations, the secretary may not award or renew contracts for Russian-designed space launch rocket engines.

The draft document also says that a waiver for the purchase of Russian-made rocket engines can also be issued if it is "necessary for the national security interests of the United States".

The 2015 National Defense Authorization Act, which funds the activities of the Department of Defense, is expected to be debated and passed in Congress next week before a December 11 deadline.

At the end of November, Capt. Chris Hoyler, a US Air Force spokesperson, told Sputnik that there had been to disruptions in the supply of Russian-made rocket engines, used to send US military satellites into space, despite the tense relations between the two countries.

With a current stockpile of 16 Russian-made RD-180 engines, the United States has enough rockets to continue launches until 2016, after which, if the supplies are stopped, there would be significant delays in the ability to launch national security satellites into space, according to an RD-180 Availability Risk Mitigation Study.

Hoyler told Sputnik that the US Air Force had not requested or received formal proposals to replace the RD-180.

The Russian-built RD-180, a successor to the Soviet RD-170, was first installed on a US Atlas III launch vehicle in 2000. It is now routinely used on Atlas V carrier rockets, which launch US military and intelligence satellites into space.