* Pentagon cleared Allen in probe following Petraeus scandal
* Allen preparing options on future US force in Afghanistan
* White House must resubmit nomination, timing unclear (Adds background, detail)
By Steve Holland
WASHINGTON, Jan 23 (Reuters) - President Barack Obama will proceed with General John Allen's nomination as NATO's supreme allied commander in Europe after the Pentagon cleared him of professional misconduct over emails to a Florida socialite, the White House said on Wednesday.
Allen, the outgoing commander of U.S. and NATO forces in Afghanistan, was ensnared in the scandal that prompted retired General David Petraeus to resign as CIA director last year after his affair with his biographer, Paula Broadwell, was exposed.
The Pentagon announced on Tuesday that an investigation launched in November had cleared Allen of any wrongdoing after looking into email exchanges between him and Jill Kelley, one of the women at the center of the Petraeus scandal.
"General Allen's nomination ... will proceed," White House spokesman Jay Carney told reporters.
"We hope the Senate will consider it in a timely manner. And, you know, we will press the Senate to do just that," Carney added.
Allen's nomination for the U.S. military's top job in Europe must be resubmitted to Congress because his original nomination expired at the end of the last congressional term, a Senate Armed Services Committee spokeswoman said.
Carney said he did not have a specific timetable for the next steps on Allen's nomination. Obama put the nomination on hold when the investigation was announced in November even as he expressed confidence in Allen's ability to serve out the final months of his command in Afghanistan.
Allen, who is married and has two daughters, has not spoken publicly since the results of the investigation were announced. He was described by an aide as pleased and focused on leading NATO forces in Afghanistan.
"He is grateful for the support he received throughout this process from his chain of command, friends, family and colleagues," an Allen spokesman, Major David Nevers, said.
Allen has been preparing options for Obama on the future U.S. military presence in Afghanistan once NATO declares the combat mission over at the end of 2014.
The White House is considering keeping between 3,000 and 9,000 troops in Afghanistan after 2014 - a lower range of options than those initially put forward by Allen.
The inquiry by the Defense Department's Inspector General centered on the emails between Allen and Kelley, a Tampa woman who knew Allen when he served as the No. 2 officer at the U.S. military's Tampa-based Central Command from July 2008 to June 2011.
Those emails surfaced when the FBI investigated Kelley's allegations of receiving anonymous, harassing emails from someone else about Petraeus. Those other emails led the FBI to uncover the affair between Petraeus and Broadwell.
Questions about the nature of the Kelley-Allen emails prompted Defense Secretary Leon Panetta to order a Pentagon investigation, a move that triggered speculation about their relationship.
Kelley, in a piece written with her husband Scott and published on the Washington Post website on Tuesday, said "the insinuation that Jill was involved in an extramarital affair is as preposterous as it is hurtful to our family." (Additional reporting by Roberta Rampton, Jeff Mason and Phil Stewart; Writing by Phil Stewart; Editing by Will Dunham)