President Barack Obama has delayed General John Allen's nomination as NATO's supreme commander pending a probe into his email correspondence with a woman at the center of a sex scandal, a White House spokesman said Tuesday.

"At the request of the secretary of defense, the president has put on hold his nomination of Gen Allen as SACEUR pending the investigation of Gen Allen's conduct by the Department of Defense IG (inspector general)," National Security Council spokesman Tommy Vietor said.

This move comes following the recent scandal in which General David Petraeus has recently been the center of a sex scandal, prompting his resignation as CIA director.

On Tuesday the Pentagon said that the top American commander in Afghanistan, General John Allen, is under investigation for alleged "inappropriate communications'' with a woman who is said to have received threatening emails from Paula Broadwell, the woman with whom Petraeus had an extramarital affair.