NATO said Tuesday it fully respected US General John Allen's decision not to take up take up command of the alliance's military forces, after weeks of speculation over his future.
In Washington, US President Barack Obama said Allen would retire instead of becoming Supreme Allied Commander in Europe so that he could take care of his family after a 19-month tour in Afghanistan.
There had been growing speculation that Allen would step aside despite being cleared of wrongdoing in a drama over emails to a Florida socialite, part of a scandal which brought down General David Petraeus as head of the CIA and his predecessor in Afghanistan.
"We fully respect General Allen's decision. As the longest serving Commander of ISAF he has shown great leadership," NATO said in a statement from its Brussels headquarters.
"The selection of a new nominee for Supreme Allied Commander in Europe is a national decision. Following a nomination by the United States, (NATO) would consider that nominee," it said.
Obama said in a statement that he had accepted Allen's request "to retire from the military so that he can address health issues within his family."
Allen told the Washington Post in an interview Tuesday that he wanted to focus on helping his wife, Kathy, who has chronic health problems that include autoimmune disorder.
He said his decision was not related to the episode over his email exchanges with a Florida woman, Jill Kelley. The Pentagon investigated the correspondence but concluded Allen had not violated rules on conduct "unbecoming of an officer", including adultery.
The probe stemmed from a scandal that forced Petraeus to resign as CIA director over an extramarital affair. Kelley had complained to the FBI about harassing emails, and authorities then uncovered an affair between Petraeus and his biographer, Paula Broadwell.
During the investigation, authorities also found emails between Allen and Kelley that were deemed potentially "inappropriate".
During his time in Afghanistan, Allen presided over a shift from counter-insurgency operations led by large numbers of US troops to efforts to advise and build up the Afghan security forces.