The US Department of Defence has reportedly refused to grant the United Launch Alliance (ULA) with the permission to use more Russian rocket engines for military and spy satellite launches.

ULA, a joint venture between Lockheed Martin and Boeing, earlier urged lawmakers to relax a ban on the use of Russian-made engines.

The US imposed a ban on the of Russian engines last year after Russia’s annexation of Ukraine’s Crimea region.

"Pentagon spokeswoman lieutenant commander Courtney Hillson said that the department remained committed to maintaining two sources of launch services."

The company had argued that it needs the waiver to compete against newly formed Space Exploration Technologies (SpaceX) in the new US Air Force (USAF) competition for satellite launches.

Recently, the Pentagon certified SpaceX to compete for national security launches, breaking ULA’s monopoly in space launches.

According to Reuters, the US Defence Department is currently seeking a number of options, including possible sole-source contract awards, in order to keep both companies in business.

Pentagon spokeswoman lieutenant commander Courtney Hillson said that the department remained committed to maintaining two sources of launch services.

She also added that its current approach will provide a platform to look for other rocket engine options as soon as possible, the news agency reported.

Currently, ULA rely on the Russian-built RD-180 engines to power its Atlas 5 rocket. With the existing contract, the company will receive rocket engines until 2019.

Meanwhile, the USAF recently started the official bidding for the development of a new prototype rocket propulsion systems, in a bid to develop a US-built system in order to stop relying on Russian engines.

In another development, the USAF recently awarded an $882m contract to ULA to continue launching satellites with its Delta IV and Atlas V rockets.

Under the contract, ULA will deliver services that include maintenance commodities, Delta and Atlas depreciation, and provides for mission assurance, programme management and systems engineering.