"He has postponed his trip so that he can monitor developments in Libya from Washington," the official said.

Gates was scheduled to depart Saturday for a three-day visit to St. Petersburg and Moscow.

Geoff Morrell, the Pentagon press secretary, told reporters waiting to depart with Gates that the trip had been delayed for at least 24 hours.

It came as France launched an air strike on a target in Libya in the first salvo of an international campaign to prevent Moamer Qadhafi's forces from crushing a month-old uprising.

World leaders gathered at a summit in Paris to plot next moves to enforce a UN resolution authorizing the use of "all necessary means" to protect civilians, impose a no-fly zone and enforce a ceasefire.