If confirmed by the Senate, Power will replace Susan Rice, who was appointed on Wednesday to be Obama’s new national security adviser. Rice will replace Tom Donilon who is stepping down in July.

Obama announced the national security team shake-up during a ceremony at the Rose Garden on Wednesday.

Obama’s selection of Rice for his top national security post was seen by many as a defiant gesture against GOP lawmakers who had been sharply critical of her response to the Benghazi Consulate attacks. That led some to question if Republicans might try to block the Power nomination as payback for Rice.

Obama on Wednesday urged senators to quickly confirm Power.

“To ensure that we have the principled leadership we need at the United Nations,” he said, “I would strongly urge the Senate to confirm her without delay.”

Power formerly served in the administration as the head of the National Security Council’s office of multilateral affairs and human rights.

Earlier in the day McCain also said while he disagreed with Rice’s selection, he was ready to work with her in that role.