"At the request of the secretary of defense, the president has put on hold his nomination of Genereal Allen as Supreme Allied Commander Europe pending the investigation of General Allen's conduct by the Department of Defence IG (inspector general)," National Security Council spokesperson Tommy Vietor said.
A US defence official said FBI investigators had uncovered a trove of 20 000 to 30 000 pages of correspondence – mostly emails – between Allen and Jill Kelley, a key figure in the scandal that brought down CIA chief David Petraeus.
"The allegations involve inappropriate communications" between Allen, the top US commander in Afghanistan, and Kelley, the official told reporters travelling with US Defence Secretary Leon Panetta.
Panetta said in a statement that his department was informed by the FBI on Sunday about the case and that he had referred it to the Pentagon's inspector general for investigation.
Allen, the top US commander in Afghanistan, had been tapped to take over as the Supreme Allied Commander Europe before the latest cascade of revelations.
"The President remains focused on fully supporting our extraordinary troops and coalition partners in Afghanistan, who General Allen continues to lead as he has so ably done for over a year," Vietor said.
Meanwhile, Obama called on the Senate to act quickly to confirm Marine Corps General Joseph Dunford as the next commander of the Nato-led force in Afghanistan, Vietor said. – Sapa-AFP