Six of the nine Republicans on the Senate Foreign Relations Committee are calling on the White House to withdraw its nomination of Brett McGurk to be U.S. ambassador to Iraq.

In a letter sent to President Barack Obama on Wednesday, the Senators wrote that “there are strong concerns about Mr. McGurk’s qualifications, his ability to work with Iraqi officials, and now his judgment.”

McGurk, 38, a former adviser to U.S. ambassadors to Iraq under both Obama and President George W. Bush, has gotten swept up in controversy over his relationship with a Wall Street Journal reporter while both were working in Iraq in 2008. Salacious emails apparently between McGurk, then married to another woman, and the journalist, Gina Chon, surfaced online last week, indicating that the two engaged in a romantic relationship while also exchanging information in their professional capacities. Chon, who is now married to McGurk, resigned from the Wall Street Journal in the wake of the revelations.

Even before the emails emerged, a number of Republicans had indicated deep reservations about McGurk’s nomination, given his lack of Foreign Service credentials or management experience. Sen. John McCain (R-Ariz.) has also been critical of McGurk’s role in negotiations last year with the Iraqis that were unsuccessful in coming up with a follow-on agreement to keep U.S. combat troops on the ground past 2011.

The letter to Obama is signed by Sens. Jim Risch (Idaho), John Barrasso (Wyo.), James Inhofe (Okla.), Jim DeMint (S.C.), Mike Lee (Utah) and Marco Rubio (Fla.).

“The U.S.-Iraq relationship is of the utmost importance to us,” they wrote, “and we respectfully request that you withdraw this nominee and nominate someone with the qualifications necessary to ensure success in this position.”

The three other Republicans on the committee — Dick Lugar (Ind.), Bob Corker (Tenn.) and Johnny Isakson (Ga.) — did not sign onto the letter. Lugar and Isakson said last week, after McGurk’s nomination hearing, that they would support his confirmation.

McGurk’s nomination is among those scheduled for a vote at the Foreign Relations Committee’s business meeting June 19, and it is expected to clear the panel with Democratic support and the two GOP votes.

On Wednesday, the White House reiterated its backing.

“In terms of Mr. McGurk, the president supports his nomination,” spokesman Jay Carney told reporters. “He put him forward. He has a great deal of experience in Iraq, not just in this administration but in the prior administration, and thinks he will serve ably as ambassador.”

But Senate Foreign Relations Chairman John Kerry (D-Mass.) acknowledged that doubts are swirling over McGurk.

“Sen. Kerry has said that there are questions and we’re in the process of finding answers and evaluating the situation,” the panel’s communications director, Jodi Seth, said Wednesday.

Last week, Risch said the nomination was bound to face significant obstacles in coming to the Senate floor and would not be able to move by unanimous consent.