NASA spokesman Glenn Mahone said O'Keefe had sent a letter of resignation to President George W. Bush earlier in the day, and it was accepted.

He was expected to leave the agency about February 1 after a successor is named, the official added.

O'Keefe is a candidate to become chancellor of Louisiana State University located in Baton Rouge, according to Mahone.

According to US media reports, the new job has a much better salary, and if he gets it, O'Keefe, who hails from southern Louisiana, will receive 500,000 dollars a year.

The list of his possible successors include General Ronald Kadish, who was in charge of the US missile defense system, former member of Congress Robert Walker as well as former astronauts Ron Sega, Charles Bolden and Robert Crippen.

O'Keefe became administrator of the National Aeronautics and Space Administration (NASA) in 2001 with the mission of cutting costs and increasing profitability.

Before NASA, he served as deputy head of the White House budget office.

But the Columbia disaster -- the shuttle disintegrated as it re-entered the Earth's atmosphere in February 2003 killing all seven crew -- forced a complete reevaluation of many NASA policies and the US space programme.

NASA has not turned the corner on this tragedy, and its three remaining space shuttles, Atlantis, Endeavour and Discovery, remain grounded while they continue to undergo modifications that the accident has made necessary.

A report published in the wake of the catastrophe detailed a number of mistakes and lax security procedures that that had occurred since the explosion of the space shuttle Challenger in 1986.

The resumption of shuttle flights is scheduled for next May, but it has already been delayed several times. The last postponement was due to four hurricanes that swept through Florida in September, causing damage at the Kennedy Space Center.

O'Keefe's successor will have to implement new goals set for the space agency by President Bush, who wants Americans to return to the Moon beginning in 2015 and to prepare for manned space flights to other planets in the solar system, including Mars.

In order to implement this plan, O'Keefe announced in June a reorganization of NASA aimed at making the agency more efficient.

To finance all of its programs, NASA received a 800-million-dollar budget increase in November -- to a total of 16.2 billion dollars

The new NASA administrator will also have to continue the work of building the International Space Station as well as make a decision on how to save the aging Hubble space telescope.

Options under consideration include organizing a manned shuttle missing to repair the device or sending out an unmanned spacecraft and rely on a robot to conduct repairs.

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