TUCSON, Ariz. — NASA officials say plans for the Phoenix Mars Lander's second day of activities on Mars have been delayed.

They say it's because of a problem in relaying communications from one of two Mars orbiters relaying commands from Earth.

Fuk Li, manager of the Mars exploration program for NASA's Jet Propulsion Laboratory in Pasadena, Calif., says that a "transient event" on the Mars Reconnaissance Orbiter turned its UHF radio off. That stopped communications between it and the lander.

But Li and others say it is not a significant problem.

Peter Smith of the University of Arizona, the mission's principal researcher, says plans called for maneuvers Tuesday to unhook the lander's 8-foot robotic arm from a latch holding it in place.