(Adds quotes from after hearing)
By Andrea Shalal
WASHINGTON, Feb 25 (Reuters) - The U.S. Air Force on Wednesday said it will release plans within months for replacing the Russian-built RD-180 motors that now power some rockets used to launch military satellites into space, but said it would likely miss a 2019 congressional deadline to start using a new U.S. engine.
Air Force Secretary Deborah James told the Senate Appropriations Committee's defense subcommittee that failure to extend the 2019 deadline could lead to swapping one monopoly provider of rocket launches for military satellites for another.
Congress last year passed a law that requires the Air Force to develop a new propulsion system by 2019 to replace the RD-180 engine that powers one of two rockets used by the current monopoly launch provider, United Launch Alliance, a joint venture of Lockheed Martin Corp and Boeing Co.
The Air Force has said it expects to certify privately held Space Exploration Technologies, or SpaceX, to launch some of those satellites by mid-year, but the process is still ongoing.
James told reporters after the hearing that she was concerned that congressionally mandated restrictions on use of RD-180 engines after 2019, coupled with the higher cost uf ULA's other rocket, the Delta 4, could hand SpaceX a defacto monopoly.
"The question is, would (Delta 4) be cost effective. If it's not, then I fear that we would inadvertently be trading one monopoly situation for another," James said. "And I don't think that's the intent of anyone in Congress."
U.S. lawmakers and military officials last year began to question U.S. reliance on Russian rocket engines for launching U.S. national security satellites after Russia annexed Crimea.
James said the Air Force was working as quickly as possible to certify SpaceX as another launch provider and develop plans for an alternate engine.
But she said the 2019 deadline was too aggressive given that it would likely take six to eight years to develop an alternate U.S.-built engine, plus another year or two to integrate the new engine with existing rockets. The total estimated cost will be around $2 billion, she said.
"The 2019 date is pretty aggressive and I'm not sure that we can make it," James said, urging lawmakers to clarify and potentially adjust the law.
ULA has said it plans to start testing a new rocket engine being designed by Blue Origin, a venture run by Amazon.com founder Jeff Bezos, from 2019. But it could take some time before that new engine is certified for satellite launches. (Reporting by Andrea Shalal; Editing by Bernard Orr)