Updated 2:03 p.m. EST on Jan. 9

WASHINGTON — The U.S. Air Force, which as of mid-December still hoped to certify SpaceX’s Falcon 9 rocket to launch national security payloads by the end of 2014, is now targeting the middle of 2015, the service said Jan. 7.

The delay, which has prompted the Air Force to re-evaluate its certification process, raises fresh doubt about SpaceX’s ability to win a competitive contract to launch a payload for the U.S. National Reconnaissance Office, operator of the nation’s spy satellites. Bids for that contract were due in August, but only certified launch services providers are eligible to win.

SpaceX has met more than 80 percent of the certification criteria under the terms of an agreement signed with the Air Force in 2013, the release said.

Meanwhile, Air Force Secretary Deborah Lee James has directed an independent team to review the new entrant certification process.

“The Air Force is committed to reintroducing competition into the extremely complex Evolved Expendable Launch Vehicle program and getting new entrants certified as soon as possible,” James said in the press release. “As with other periodic looks we’ve done over the years, we will further assess whether we can streamline and improve the certification process while protecting launch mission assurance. To that end, I am directing a review of our new entrant certification process by an independent team to capture the lessons learned so we can enhance competition for launch services.”

That study is expected to be completed this summer, said Capt. Chris Hoyler, an Air Force spokesman.

The Air Force press release followed a Jan. 6 release that acknowledged the certification delay and announced the review but did not include any information about when SpaceX might complete the process. The revised press release said certification is now expected no later than mid-2015.

Air Force officials had repeatedly said they wanted to certify Falcon 9 in time to allow SpaceX to compete for the NRO launch, the award of which is imminent, according to industry sources. It now appears that the contract, barring a significant delay, will go to United Launch Alliance, currently the only company certified to launch operational U.S. national security satellites.

Air Force officials had hoped to award a contract by the end of 2014.

“In a relatively short period of time, SpaceX has made historic progress as a launch provider and helped prove how effective competition can be in the civil space industry, all while bringing commercial space launches back to the United States,” Lt. Gen. Samuel Greaves, commander of the Space and Missile Systems Center at Los Angeles Air Force Base, said in the press release.

John Taylor, a SpaceX spokesman, did not return phone calls seeking comment.

As part of its plan to reduce its satellite launching costs and mollify critics of ULA’s current monopoly in the national security launch market, the Air Force in 2012 ordered a large batch of rockets on a sole-source basis from that company, a Boeing-Lockheed Martin joint venture, while setting aside an additional seven to eight missions for competition.

Hawthorne, California-based SpaceX, which is expected to bid on the competitive missions, is also challenging ULA’s contract, whose estimated value is $11 billion, in a lawsuit filed in federal court in April.

SpaceX has submitted data from three of its launches — as required — for certification and completed a series of 19 engineering review boards as part of the process, Air Force officials have said. Greaves has been reviewing the materials since mid-December before making a final decision. Thus far, the service has dedicated more than $60 million and 150 people to the certification process.

In a 2013 report, the U.S. Government Accountability Office, Congress’ watchdog agency, said certification has been complicated by Air Force changes to the technical requirements for integrating satellites with their launch vehicles.