(AP) -- Clouds prevented space shuttle Endeavour from blasting off Sunday on the last planned nighttime shuttle launch, delaying its trip with a final few building blocks for the International Space Station.
The band of low clouds started moving in from the north late Saturday. NASA counted down to the nine-minute mark, but the sky remained overcast, offering little hope of a lucky break.
NASA managers said they would try again Monday, when slightly better conditions were expected.
"We tried really, really hard to work the weather. It was just too dynamic," launch director Mike Leinbach told the six astronauts aboard Endeavour. "We just were not comfortable with launching a space shuttle tonight."
"Sometimes you just got to make the call," replied commander George Zamka. "So we understand and we'll give it another try tomorrow night."
An hour later, the astronauts crawled out of the shuttle, one at a time.
Endeavour is loaded with a new room for the space station, as well as an observation deck. Once both of those are installed, the orbiting complex will be 98 percent complete.
Launch time on Monday is scheduled at 4:14 a.m. That means the launch team will have to report to work right around Super Bowl time. Leinbach said late last week that his launch controllers knew going in that it might come to this, and that they might have to miss the game.
It's expected to be the last shuttle launch in darkness. The pre-dawn departure will mean the graveyard shift for Zamka and his crew during the entire 13-day flight.
NASA Administrator Charles Bolden reminded journalists Saturday that there are only five shuttle missions left.
"You're going to have to figure out what else you're going to do, along with us," he said.
In an hourlong news conference, Bolden accepted the blame for the way the NASA work force was informed of President Barack Obama's plans to dismantle the Constellation moon exploration program. In the proposed budget that was released Monday, Obama set NASA on a new post-shuttle path. Specifics were lacking, but the moon was no longer at the forefront. Neither were the Ares rockets that NASA had been working on for so long.
Shuttle managers on Friday used the words "shock" and "angst" to describe their colleagues' mood.
"Why wasn't the NASA work force better prepared for this?" Bolden said. "You're looking at the guy who's responsible. I will take the heat."
Bolden, a former shuttle commander, said he did not listen to his advisers on how to present the information, and has spent the past few days apologizing to everyone. "I was stupid, I admit that. I didn't do it right," he said.
As for the future, Bolden said the country needs a big rocketship to carry heavy loads if astronauts are to venture beyond Earth's orbit. He said he wants to use the lessons of Constellation to capture new technologies and build that rocket.
"While we will phase out the Constellation program per se, I don't want to throw away the baby with the bath water," he said.
Bolden said he envisions such a rocket - capable of carrying astronauts to the moon, Mars or asteroids - ready to fly sometime between 2020 and 2030. He personally favors Mars.
Whatever the destination or rocket, the new way forward will be "significantly better than what we got rid of," Bolden said.
Explore further: Space shuttle Endeavour cleared for Sunday launch