WASHINGTON — NASA is delaying a mission to Mars that already had been over budget and will get even more costly.

The launch of the massive roving robot with a rock-zapping laser was pushed back Thursday from next year until 2011, adding $400 million to the price tag. More than 10 different problems, all solvable with time, forced the postponement, Mars exploration chief Doug McCuistion said.

The six-wheeled Mars Science Laboratory is designed as the most powerful spacecraft to explore the Martian surface. About the size of a small sport utility vehicle, it will probe the red planet's climate and geology in finer detail than previous missions.

The project has been dogged by cost increases and technical challenges. Just two years ago the lab was supposed to cost $1.6 billion; the launch delay inflates the price to nearly $2.3 billion.

The biggest major technical problem involves motors and gear boxes that will help the rover drive around and bend its robotic arm to reach out to test soil. One of the most vexing problems: the brake sticks in the on position in cold weather, McCuistion said. Other problems involved cracks in a key pipe, computer glitches and easy-to-fix failures with solar power cells, he said.

The problems couldn't be fixed and tested in time to launch next year, NASA Administrator Michael Griffin said. "Despite the delay, work on the mission really is progressing well with the exception of the motor problem," he said.

Mars and Earth only pass close enough to launch probes every 26 months. The next opportunity is September and October next year; it will be the first time since 1994 that NASA will miss a chance to launch toward Mars.

Sean Solomon of the Carnegie Institution of Washington, who heads a NASA Mercury mission, thinks the space agency made the right choice to slip the Mars launch, but he warned it could hurt other projects.

"That's quite a high price to pay for this delay. We're not in a good place on this mission," said Solomon who chairs the planetary subcommittee of NASA's Advisory Council.

It is the second time in two years that NASA has postponed a Mars mission. Last year, it delayed a planned 2011 launch of a $485 million Mars atmospheric probe by two years because of an unspecified conflict of interest in the selection process.