A United Launch Alliance Atlas V rocket carrying the Morelos-3 spacecraft lifted off from Space Launch Complex 41 at Cape Canaveral on Oct. 25. (Courtesy of ULA)

It was, as usual, a spectacular display of fire and force, a rocket blast lighting up the still dark sky shortly before dawn. The launch from Cape Canaveral Friday was historic, too— the 100th for the United Launch Alliance, a  milestone that the company cheered as a symbol of its long heritage in space.

But it came at a perilous time for ULA, the joint venture between Lockheed Martin and Boeing, which for years has had a monopoly on launching Pentagon payloads to space.

ULA is facing a challenge from SpaceX, the hard-charging upstart founded by billionaire entrepreneur Elon Musk, which just won certification by the Air Force that would allow it to compete against ULA for the next Pentagon launch contract.

And ULA faces an even bigger problem: the Russian-made rocket engine it relies on has been entangled in a messy political fight that could threaten its ability to compete at all.

[ULA ready to compete against Elon Musk’s space startup, CEO says]

As a result of the tensions with Russia, Congress banned the use of the RD-180 engine, which powers ULA’s Atlas V rocket, for national security launches starting in 2019. ULA is working with Blue Origin, the space company founded by Amazon.com founder Jeffrey P. Bezos, to develop a U.S.-made engine. (Bezos owns The Washington Post.)

But that engine, the BE-4, won’t be ready for another few years, and to bridge the gap, ULA Chief Executive Tory Bruno said the company needs at least 14 RD-180 engines.

In its most recent spending bill, Congress has proposed allowing the company to use four.

In a call with reporters Friday, Bruno said that was “a good start” but ultimately “insufficient” to allow the company to compete.

While ULA had five other RD-180s it could have used, Bruno said those were allocated to other missions. “Those five are gone,” he said.

He declined to comment on Aerojet Rocketdyne’s recent $2 billion bid to acquire ULA, which was rebuffed.

The restriction on the Russian engines is also causing concern at the Pentagon, which wants to introduce competition into the contract and bring down the cost. Claire Leon, the Air Force’s launch enterprise director, told reporters Friday that, “it is critical to the Air Force that we get more than one bidder. We are actively working to make it possible for ULA to bid. That’s in the works at the highest levels at this point.”

She said senior officials are working with Congress to loosen the restriction and have been pushing for Congress to allow the use of 18 RD-180s. They are also working with the office of the Secretary of Defense, which could also grant ULA a waiver that would allow it to use more RD-180s in what’s known as the Evolved Expendable Launch Vehicle program. ULA could also use the five engines it reallocated for other missions, she said.

“The whole purpose is to reduce cost and get companies to operate at the lowest price point as possible,” she said.

Loren Thompson, a defense consultant who works closely with Lockheed Martin and Boeing, said that Congress “may be in the process of unraveling its most reliable launch provider. No company in history has a better launch record, and yet all the political pressures on ULA are severely undermining its business strategy.”

In a statement, John Taylor, a SpaceX spokesman, said that the company “applauds the Air Force for reintroducing competition into the EELV Program, which will improve assured access to space and result in best value for the government and the taxpayers for the first time in over a decade.”

Bids are due next month, and the contract is expected to be awarded in March. Leon would not say how much it is expected to be worth but that officials anticipate it to be lower than the average of $140 million per launch the Pentagon pays ULA under the current sole-source contract.

The contract would be to launch the Pentagon’s next-generation GPS III satellite, which has improved navigation accuracy and anti-jamming capabilities. Air Force officials expect it to launch in 2018.