The US Air Force (USAF) has reportedly started the official bidding for the development of new prototype rocket propulsion systems.

According to USAF Space and Missiles Systems Center head Lieutenant General Samuel Greaves, the government is planning to divide $160m contracts among four bidders on a rolling basis, Reuters reported.

This new development is aimed to develop a US-built system in order to stop relying on Russian engines to launch military and intelligence satellites.

Under this public-private partnership programme, the companies will be required to depend on their own funds to cover a third of the cost of the prototype development, Greaves added.

"The US Government is planning to divide $160m contracts among four bidders on a rolling basis."

Greaves was quoted by the news agency as saying: "We’re moving fast. The plan is to transition from the RD-180 by investing with industry partners to develop commercially viable launch systems that also assure access to space for our (national security space) systems."

The initial proposals were due by June 23 and the contracts are expected to be awarded from September.

Recently, Russia banned the export of rocket engines to the US to launch military satellites in the wake of disputes raised after Moscow’s annexation of Ukraine’s Crimea region.

Currently, United Launch Alliance (ULA), a joint venture of Lockheed Martin and Boeing rely on the Russian-built RD-180 engines to power its Atlas 5 rocket. However, ULA will receive rocket engines that are already ordered until 2019.

ULA is planning to shift some satellites onto pricier Delta 4 rockets once it runs out of RD-180s.

Reuters said ULA is expected to compete with SpaceX, the company that was recently certified to compete for military and spy satellite launches.