Thunderstorms forced NASA to call off Saturday’s launch of Discovery, delaying the first space shuttle flight in a year by a day.

More bad weather was forecast for Sunday and for the rest of the Independence Day weekend. Storm clouds moved in and out of the launch zone throughout the morning and early afternoon. As the countdown held at the nine-minute mark, it became clear the weather would not improve, and launch director Mike Leinbach announced a one-day delay.

“We’re not going to make it today,” Leinbach said. “It’s not a good day to launch, so we’re going to try again Sunday.”

The seven astronauts aboard the fueled spaceship immediately began backing out of their launch procedures. “It wasn’t our time today, and we’ll launch when we’re ready and hopefully, tomorrow will look better,” shuttle commander Steven Lindsey replied.

NASA had just five minutes to launch the shuttle Saturday because of the need to intercept the international space station in orbit. The next launch attempt was scheduled for 3:26 p.m. EDT Sunday.

The delay was a disappointment for NASA, which last flew the shuttle last July and was eager to get flights to the international space station back on track. Among the space agency’s guests at the launch were Vice President Cheney and several members of Congress.

The only technical problem that popped up during the countdown Saturday was a failed heater for one of Discovery’s thrusters, needed to keep the fuel from freezing. Mission managers decided to proceed with the launch, since the thruster was not needed during liftoff.