Launch of the Opportunity probe had been set for late Sunday. It was moved to Monday at either 10:35 pm (0235 GMT Tuesday) or 11:18 pmTuesday), NASA said in a statement.

"The delay is due to the failure of a battery cell associated with the component of a launch vehicle flight termination system. The battery must be removed or replaced," the statement said.

NASA said there was a 30-percent chance weather may force another postponement of the launch.

Opportunity was originally set for launch June 25, but its flight has been repeatedly delayed by weather and technical problems.

NASA conducted tests of the Delta II rocket to determine if the cork insulation had separated from a turbine. They found that some isolated separation of the cork.

"After the tanking inspections revealed some selective debonding of the corks from the surface of vehicle within a limited area.

"The locations are being repaired using a different adhesive ... this problem has been resolved (on Saturday night) at the satisfaction of engineers."

Spirit, the first of the twin probes in the US mission, took off June 10. It should arrive on Mars next January.

Last weekend, strong winds halted the launch set for Saturday and later for Sunday.

Liftoff is from Cape Canaveral next to the Kennedy Space Center in the southeastern US state of Florida.

NASA has until July 15 to launch Opportunity. After that date, the red planet moves out of range for an Earth launch.

The US mission comes on the heels of a European mission begun June 2 with the Mars Express probe, now on its way to Mars.

If NASA manages to launch its second probe Monday night, it will travel 491 million kilometers (30.5 million miles) in seven months, arriving on the Martian surface about January 25.

Spirit, the first probe, is headed for the Gusev Crater, 15 degrees south of the Martian equator.

Opportunity is bound for a seven-month journey through space. Its touchdown target is the Meridiani Planum, a zone containing a concentration of ferrous oxide situated two degrees south of Mars' equator.

Although both probes will set down relatively close to the Martian equator, they will be on virtually opposite sides of the planet, some 6,000 miles (9,600 kilometers) apart.

NASA is investing some 800 million dollars on two six-wheeled vehicles, which for three months are to look around sites considered geologically important, searching for clues that water may once have flowed on Mars, which could increase the likelihood that there was once life.

SPACE.WIRE