But Ms. Kosmas argued that commercial rockets should be a complement to a NASA-led program, not a replacement.

Debate on the future of NASA’s human spaceflight program will continue through the summer as the administration and Congress try to arrive at a compromise.

In recent weeks, SpaceX has tried to play down the significance of the first Falcon 9 launching. “I hope people don’t put too much emphasis on our success,” Mr. Musk said Thursday at a news conference, “because it’s simply not correct to have the fate of commercial launch depend on what happens in the next few days. But it certainly does add to the pressure. There’s more weight on our shoulders because of that. I wish there weren’t.”

After the flight, Mr. Musk said it was “to a significant degree a vindication of what the president has proposed.”

SpaceX is aiming to launch a second Falcon 9 this summer to demonstrate its capabilities for NASA before it gets the go-ahead to take cargo and supplies to the International Space Station. That flight will include an operational version of the Dragon capsule, which will hold cargo and, eventually, astronauts. That capsule would not go to the space station but would demonstrate orbital maneuvers and return to Earth.

The third Falcon 9 flight has been pushed back about five months to March 2011 at the earliest. However, Mr. Musk said he would like to expand its objectives so that the Dragon capsule could go all the way to the space station, perhaps even carrying cargo. That objective had been scheduled for the fourth flight.

SpaceX won a $278 million contract from NASA in 2006 for the demonstration flights, and, if successful, it would move on to a $1.6 billion contract for 12 flights to take supplies to the space station.