U.S. lawmakers have called for a program to develop a next-generation liquid-fuel rocket engine within five years, proposing legislation aimed at reducing U.S. dependence on Russian engines to launch military and spy satellites.

United Launch Alliance, a joint venture of Lockheed Martin and Boeing, currently uses the RD-180 rocket engine made by Russia's NPO Energomash to launch Atlas V rockets carrying U.S. military and spy satellites.

Air Force Undersecretary Eric Fanning told lawmakers last month that America has enough engines to support launches well into 2016.