The last man on the moon, Eugene A. Cernan (search), said Wednesday he knew he wouldn't hold that distinction forever.

"I've been waiting for this day for 31 years," said Cernan, who was in the audience at NASA headquarters when President Bush outlined his proposal to continue America's journey into space with manned missions to the moon, to Mars (search) and to worlds beyond.

Bush singled out Cernan and quoted what the astronaut said when he left the lunar surface: "We leave as we came, and God willing as we shall return, with peace and hope for all mankind."

"America will make those words come true," the president said.

Cernan, now 69, was commander of the Apollo 17 (search) mission and set foot on the lunar surface in December 1972.

Cernan said that when he returned to Earth, he believed that America would someday launch new missions to the moon. "I said we're not only going to go back to the moon, we'll be on our way to Mars by the turn of the century."

"I was a little wrong in my timetable," he said, "but my glass was never half empty, it was always half full, and today the president allowed us a taste of what was in that glass."

Although Bush did not set a timetable for a Mars mission, aides said it would be later this century, sometime after 2030.

The Apollo 17 mission was Cernan's third space flight. All told, he logged 566 hours and 15 minutes in space during his career, of which more than 73 hours were spent on the moon's surface, according to NASA.