WASHINGTON (AP) — President Barack Obama has tapped former Pentagon No. 2 Ashton Carter to be his next defense secretary and carry out the U.S. military effort against the Islamic State in Iraq and Syria, a senior Republican senator said Tuesday. White House officials, however, insisted no final decision has been reached.

Sen. Jim Inhofe of Oklahoma, the Senate Armed Services Committee's top Republican, said he was informed of the decision Tuesday morning. He said he backs Carter's nomination.

"I support it very strongly," Inhofe said. "I'm very pleased he is going to be our secretary of defense. I can't imagine that he's going to have opposition to his confirmation."

Carter is a former deputy defense secretary. If confirmed, he would replace Chuck Hagel, who announced his resignation last week.

The White House wouldn't confirm that Obama has made his choice, though officials have described Carter as the top candidate.

The next Pentagon chief will be entrusted with taking over a sprawling department that has had an uneasy relationship with the White House.

Carter, 60, moved to the top of the White House's short list after several leading contenders pulled their names from consideration. Carter is well-respected both in the West Wing and at the Pentagon, where he served until last year. He also has support among Republicans — of great importance given that Republicans will take the majority next month.