United Launch Alliance is trying to fight back against critics of its Russian-made rocket engine.

The company announced Wednesday they're partnering up with aerospace company Blue Origin to fund and develop an American-made rocket engine.

Blue Origin has been working on the BE-4 engine for three years. Thanks to financial support from ULA, the company hopes they can begin testing the rocket in 2016 with the first flight in 2019.

The BE-4 is a liquid oxygen, liquefied natural gas rocket engine.

Critics, including ULA's biggest competitor SpaceX, have slammed the rocket company for using a Russian-made engine on its Atlas V rocket.

At the high point of tensions between Russia and the U.S. over Ukraine earlier this year, Russia threatened to stop delivery of the engine because a majority of Atlas V's missions are for the U.S. government. That threat never came to fruition.

Blue Origin was created by the founder of Amazon.com, Jeff Bezos.

Like SpaceX, the company is hoping to fly humans to space before the end of the decade.