WASHINGTON — The Obama administration’s pick to be the next ambassador to Iraq withdrew his nomination today amid opposition from Senate Republicans concerned that he may have engaged in improper behavior while working at the U.S. Embassy in Baghdad in 2008.

In a letter to President Barack Obama and Secretary of State Hillary Rodham Clinton, Brett McGurk said he was removing himself from consideration for the job with a “heavy heart.” He said he was doing so after consulting with his wife, Gina Chon, because he believed it was in the “best interests of the country, and of our life together, to withdraw my nomination and serve in another capacity.” The AP obtained a copy of the letter.

McGurk’s nomination, which was to have been voted on Tuesday by the Senate Foreign Relations Committee, had become controversial following the release on the Internet earlier this month of sometimes racy emails he sent to a female Wall Street Journal reporter while he was negotiating a security agreement with the Iraqi government during President George W. Bush’s administration.

The emails in question indicate that McGurk had an intimate relationship with the journalist, Gina Chon, while he was married to another woman. McGurk has since married Chon, who resigned from The Wall Street Journal last week after acknowledging that she violated in-house rules by showing McGurk unpublished stories.

In the letter, McGurk said Iraq badly needs a U.S. ambassador to succeed outgoing envoy James Jeffrey, but that the furor over the emails was a distraction that would delay the replacement. He said the controversy over the emails was a major part in his decision to withdraw.

“The most difficult part of this process, however, was watching my wife become a part of it,” he wrote. “She is the most precious thing in the world to me, and the depiction of our relationship has been both surreal and devastating.”

Six Republican members of the Senate Foreign Relations Committee asked Obama last week to withdraw McGurk’s nomination citing concerns about his abilities and judgment, noting in part the emails.