The Obama administration's pick to be the next ambassador to Iraq is withdrawing his nomination amid concerns that he engaged in improper behavior while working at the U.S. Embassy in Baghdad in 2008.

In a letter sent Monday 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.

Senate Republicans last week asked Obama to withdraw McGurk's nomination citing concerns about his abilities and judgment.