With the space shuttles due to retire, NASA is looking for private companies interested in taking over the potentially lucrative business of flying cargo and crew to the international space station.

The U.S. space agency issued a long-awaited announcement Tuesday for firms interested in handling delivery services now provided by the three shuttles, which are due to stop flying by 2010.

“Certainly this is an opportunity for the new space companies,” said Jim Banke, head of Florida operations for The Space Foundation, an industry trade association. “They’ve been lobbying NASA hard for something like this for years.”

NASA hopes to supplement, and eventually replace, crew and cargo flights to the space station that had been planned for the shuttle fleet. The agency also may have to pare down the number of shuttle flights to the station even before they retire to pay for development of a new spacecraft known as the Crew Exploration Vehicle.

In addition to flying to the station if no commercial providers are available, the Crew Exploration Vehicle is being designed to carry astronauts to the moon.

“We’re excited about this opportunity,” said Larry Williams, who handles international and government affairs for Space Exploration Technologies, or SpaceX. The California-based is planning its debut rocket launch from Kwajalein Atoll in the Pacific this month.

SpaceX was founded and funded by Internet entrepreneur Elon Musk, who sold his online payment services firm PayPal to eBay for $1.5 billion.

Musk is developing a series of launchers, called the Falcon, which, if successful, could significantly undercut the price routinely paid to aerospace giants Lockheed Martin Corp. and Boeing Co., to send payloads into orbit.

Other start-up firms that have expressed interest in NASA’s space station business include t/Space, SpaceDev, Constellation Services International, AirLaunch LLC, SpaceHab, Andrews Space, Rocketplane Ltd., Universal Space Lines and Bigelow Aerospace, according to an Excel spreadsheet on NASA’s procurement Web site.

Boeing and Lockheed Martin, which manufacture and sell the Delta and Atlas expendable launch vehicles, have kept any aspirations of becoming NASA’s space station truckers under wraps.

“As long as it’s a level playing field, we’re open to compete with them any time and anywhere,” said SpaceX’s Williams.

Companies have until Feb. 10 to submit proposals to NASA for its transport services. The agency expects to award one or more contracts in May. NASA has allotted $500 million to pay for the initial phases of the program through 2010.