US General John Allen has decided to retire rather than proceed with his nomination as the NATO supreme allied commander, Barack Obama, the US president, has said.
"I wish him and his family the very best as they begin this new chapter, and we will carry forward the extraordinary work that General Allen led in Afghanistan," Obama said in a statement on Tuesday.
Obama praised the general's performance in Afghanistan, where he oversaw the start of the withdrawal from America's longest war.
"John Allen is one of America's finest military leaders, a true patriot, and a man I have come to respect greatly," Obama said after meeting the general earlier in the day.
General Allen, the former commander of NATO-led forces in Afghanistan, was investigated for alleged inappropriate communication with a Florida socialite at the centre of a scandal involving former CIA Director David Petraeus, who was forced to resign in November last year.
He was cleared of misconduct by Pentagon investigators over emails he sent to the woman, who knew Allen when he served as the number-two officer at the US military's Tampa-based Central Command from July 2008 to June 2011.
Allen, in an interview with the Washington Post newspaper, said he wanted to focus on helping his wife cope with chronic health issues that include an autoimmune disorder.
"For a long time, I told her, 'When you can't bear this anymore, just tell me and I'll drop my [resignation] letter right away,'" Allen was quoted as saying by the Post.
The paper said Allen, who has two daughters, no longer wanted to place the pressure for that decision on his wife.
The four-star general, who took over command in Afghanistan in July 2011, was succeeded by General Joseph Dunford earlier this month.