WASHINGTON — Just days after United Launch Alliance dropped out of the Pentagon's competition to send satellites into space, the chairman of the Senate Armed Services Committee accused the Boeing and Lockheed Martin joint venture of attempting to "manufacture a crisis" for military space launch.

"Recent attempts by the incumbent contractor to manufacture a crisis by prematurely diminishing its stockpile of engines purchased prior to the Russian invasion of Crimea should be viewed with skepticism and scrutinized heavily," Sen. John McCain, R-Ariz., wrote in a Thursday letter to Senate Appropriations Committee Chairman Thad Cochran, R-Miss.

ULA's dropping out of the Air Force's GPS III Launch Services completion, a crucial phase of the Evolved Expendable Launch Vehicle program, should not be "misconstrued" as a reason to undermine planned sanctions on Russia, McCain warned.

By bowing out, ULA made good on its threat to skip the competition unless it got relief from the Fiscal Year 2015 defense budget's ban on the use of Russian RD-180 rocket engines for military satellite launches after 2019. ULA, which relies on the Russian RD-180 rocket engine to power its Atlas V rocket, earlier this year begged the Defense Department for some relief from the ban, which was established in response to Moscow's annexation of Crimea last year. But the Pentagon refused.

McCain's letter is a response to efforts by Sen. Richard Shelby, an Alabama Republican and member of the Appropriations Committee, to add language to a massive federal spending bill that would allow ULA to keep buying RD-180 engines from Russia until a domestic alternative is available. Alabama is home to a massive ULA rocket factory.

"Sen. Shelby is currently evaluating how the omnibus appropriations bill could ensure that, until an American-made rocket engine to replace the RD-180 is developed, the Air Force has access to the RD-180 to guarantee America's access to space, eliminate a possible national security risk, and secure approximately 800 jobs in Alabama," Shelby spokeswoman Torrie Matous said in a Thursday email.

Shelby is concerned about a minimum six-year gap in guaranteed access to space due to the 2015 ban, according to a July 15 letter he wrote to US Air Force Secretary Deborah Lee James.

The Air Force needs up to 18 RD-180 engines through fiscal year 2022 to ensure access to space and enable competition, the service's outgoing acquisition chief William LaPlante wrote in a July 16 response.

"We believe authorization to use up to 18 RD-180 engines in the competitive procurement and award of launch service contracts through Fiscal Year 2022 is a reasonable starting point to mitigate risk associated with assured access to space and to enable competition," LaPlante wrote.

McCain emphasized that Congress earlier this month approved a defense authorization bill that allows ULA to use nine RD-180 engines during the transition to non-Russian propulsion systems — four more than allotted last year.

However, those engines are tied up in other missions, Shelby's office told Defense News on Friday.

Elon Musk's SpaceX, now the sole bidder on the GPS III contract, has argued that nothing is preventing ULA from ordering more RD-180 engines for commercial or civil missions, as the ban only applies to military launches. ULA could then use the already-approved engines for the GPS III competition.

But it takes 18 months to three years to get new Russian rocket engines, representatives from Shelby's office argued. The commercial launches are "ready to go" and can't wait for ULA to obtain new RD-180s.

ULA does build another rocket, the Delta IV, which is powered by US company Aerojet Rocketdyne's RS-68 engine. But this rocket is much heavier and more expensive than the Atlas V, and not price-competitive for the GPS III launch, Shelby's office said.

The Delta IV is like "driving a Rolls Royce when you might need a Toyota," a representative said.

ULA also recently announced they are building a new rocket, the Vulcan, which will be powered by Blue Origin's homegrown BE-4 engine. But the BE-4 won't be ready to compete for several years, ULA has said.

In the meantime, ULA's surprise pullout paves the way for SpaceX to win its first military space launch contract. SpaceX's Falcon 9 rocket won certification earlier this year to compete for military space launches.

However, Shelby's office said the Falcon 9 is only certified for some of the military launches Atlas V can do. The Falcon 9 does not have sufficient engine thrust to be able to compete for launches such the Advanced Extremely High Frequency (AEHF) system, WideBand Global SATCOM, and the Mobile User Objective System (MUOS), as well as five classified missions, a representative said.

Shelby's office also noted that SpaceX's Falcon 9 exploded during a June 28 mission to resupply the International Space Station — just weeks after SpaceX won military launch certification.

Falcon 9 can execute roughly 60 percent of national security space launches today, SpaceX Chief Operating Officer Gwynne Shotwell told Congress earlier this year. SpaceX is working to upgrade the existing rocket, and is also working on a Falcon 9 "Heavy" that will have greater thrust. Falcon 9 and Falcon Heavy will be able to execute 100 percent of EELV missions, Shotwell said, adding that Falcon Heavy will be certified well in advance of any competitions for missions that would require its capability.

Shelby is not a proponent of relying on Russian rockets, Matous stressed. Shelby, a member of the Senate Appropriations Committee, worked to include $143.6 million in this year's defense appropriations bill for development of an alternative engine, in addition to the $220 million that was already included last year, she said.

Pentagon press secretary Peter Cook declined to comment on the GPS III source selection process during a Nov. 17 briefing. An Air Force spokeswoman also declined to "speculate" on a contract that has not yet been awarded.

Twitter: @laraseligman