Space shuttle Discovery has two problems — a fuel tank sensor that misreads and a robotic arm that was dinged — that could potentially delay its planned launch in May.

No decision has been made on whether those predicaments will push back the launch of the second shuttle mission since the doomed Columbia flight in 2003, NASA spokesman Kyle Herring said Tuesday.

But last week, NASA officials said that sticking to a May launch schedule provided little time to fix any major technical problems. Space shuttle program manager Wayne Hale plans to hear a formal presentation from tank project managers before deciding what to do.

"The program hasn't heard the full story," Herring said. "It's very premature to indicate that we're going to do anything with this right now."

The fuel tank problem was discovered during testing before it was shipped to the Kennedy Space Center in Florida last week. One of the four sensors at the bottom of the liquid hydrogen fuel tank gave an electrical current reading that was slightly off.

The fuel sensors are used for making sure the spacecraft's main engines shut down during the ascent when the tank runs out of fuel. A launch could end in tragedy if the engines cut out too early or too late.

Last year, the launch of Discovery was delayed because of a malfunctioning hydrogen fuel sensor. NASA never was able to pinpoint the cause and was prepared to fly with just three of the four fuel sensors working but the problem never resurfaced on launch day.

Options for the current problem include flying with just three sensors working properly or swapping out parts, although engineers hope they don't have to open up the tank.

"It's like your car," Herring said. "If you open up your engine to try to find a small problem, you might create some others."

Discovery's robotic arm was bumped last Saturday by a cherry-picker-type vehicle that was being used to clean up broken glass from a light bulb whose pieces had fallen in the shuttle's open payload bay. Engineers haven't decided whether the arm will need to be changed out.