On April 30, SpaceX will break United Launch Alliance's 10-year monopoly on military launches when it puts a satellite into orbit for the National Reconnaissance Office. The company completed a static test fire of the rocket April 25.

CAPE CANAVERAL, Fla. — SpaceX is preparing to launch a classified spacecraft into orbit on a Falcon 9 rocket for the National Reconnaissance Office (NRO) on Sunday (April 30), breaking United Launch Alliance's 10-year monopoly on launching U.S. military and national security satellites.

The rocket is slated to lift off between 7 and 9 a.m. EDT (1100 to 1300 GMT) from the Kennedy Space Center in Florida. The launch will mark the fifth of more than 20 Falcon 9 rockets slated to fly this year.

SpaceX will attempt to land the rocket's first stage just south of the NASA spaceport at Cape Canaveral Air Force Station, where three boosters have successfully touched down after dispatching spacecraft into orbit. [SpaceX Launches from Historic Launch Pad 39A (Video)]

A month ago, SpaceX launched one of its previously flown rockets for the first time, a key step in company founder and chief engineer Elon Musk's quest to slash launch costs.

SpaceX battled for years to win the right to compete for the military's launch business, ultimately suing the Air Force, its prospective customer, to break United Launch Alliance's monopoly. United Launch Alliance, a partnership of Lockheed Martin and Boeing, has flown nearly all of the country's major military and national security spacecraft since its formation in December 2006.

In addition to the upcoming NRO mission, which the agency disclosed last year, SpaceX has won two launch contracts from the Air Force to put GPS-3 satellites into orbit. ULA did not bid for the first contract, which was awarded last year, and lost to SpaceX for the second, which was awarded last month.

In an effort to foster competition and lower prices, the Air Force told reporters last month that it intends to solicit bids for as many as 13 more launches. ULA's exclusive $11 billion, block-buy contract with the military (a single contract covering a bulk of core launch vehicles) is scheduled to end in 2019.

SpaceX and the NRO have not disclosed what is being carried aboard the Falcon 9 rocket slated to fly on Sunday, nor the exact launch time. SpaceX conducted a routine test fire of the rocket's first stage on Tuesday.

Editor's note: SpaceX will provide a live webcast of its first U.S. military satellite launch on Sunday, April 30. The webcast will start at about 6:40 a.m. EDT (1040 GMT) for the 7 a.m. EDT (1100 GMT) launch window opening. You can watch it directly from SpaceX here, or here at Space.com, courtesy of SpaceX.

Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.