The US Department of Defense will reply to the letter of US Senate Armed Services Committee Chairman John McCain regarding the using of Russian RD-180 rocket engines, Department spokesperson Maureen Schumann told Sputnik.

On Wednesday, McCain sent a letter to Defense Secretary Ashton Carter in which he said the Armed Services Committee will assess a possibility to completely prohibit the use of teh RD-180 engines.

"The [Defense] Department has received the letter from Senator McCain and will respond promptly and directly to him," Schumann stated on Thursday.

In 2014, Congress passed a law requiring the United States to develop a domestically produced next-generation rocket propulsion system by 2019 in order to eliminate reliance on the Russian RD-180 rocket engines.

Developing an alternative rocket will take the United States five to seven years because of technological challenges, resulting in a two to five year gap in the ability to launch payloads, according to the US Air Force.

Earlier in November, US Air Force Secretary Deborah Lee James stated that the Air Force is working with Congress to ease restrictions on using the Russian rocket engine.

When reached by Sputnik for comment on McCain's letter, United Launch Alliance (ULA), a joint Boeing-Lockheed Martin venture providing rocket launch services to the US government, said they did not have a comment.

In January, Russian rocket producer Energia signed a $1 billion contract with US Orbital Sciences Corporation for the delivery of 60 RD-181 engines.

Source: Sputnik News