The president's pick to be the next secretary of the Army may never get to serve in that role because of a Republican senator's opposition to closing Guantanamo Bay.

Sen. Pat Roberts, R-Kan., told the Topeka Capital-Journal last week that he has placed a hold on the confirmation of Eric Fanning and intends to do so for the remainder of this year.

"I want to stress that it's nothing personal," Roberts said. "It's just the way it is."

Roberts said the hold is over the president's plan to bring some detainees to the United States to close Guantanamo Bay before the end of his term. A Pentagon team visited several sites last year to assess the cost of housing high-risk detainees at United States facilities, including Fort Leavenworth in Roberts' home state.

Sen. John McCain, R-Ariz., and chairman of the Senate Armed Services Committee, told reporters earlier this month that he thinks Fanning's nomination should move forward on its own merit and not be tied to Guantanamo. But Senate rules allow just one senator to stop a nomination from moving forward.

Fanning appeared before the Senate Armed Services Committee last week for his confirmation hearing, where he discussed Army troop levels and the fight against the Islamic State. He is widely seen as being qualified to lead the Army after formerly serving as the acting undersecretary of the Army and the chief of staff to Defense Secretary Ashton Carter.

Fanning would also be the first openly gay service secretary if confirmed.

Fanning was previously serving as the acting secretary of the Army while awaiting his confirmation, but stepped aside earlier this month after McCain alleged that acting in a role for which he was not yet confirmed is illegal under the Vacancies Act.

The Pentagon disagreed that the move broke the law, but complied nonetheless to speed up Fanning's confirmation.

Patrick Murphy, the newly confirmed undersecretary of the Army, is serving as the acting secretary until Fanning is confirmed.