Arizona Sen. John McCain on Sunday said he's still uncertain about whether President Trump will lead a successful administration.

Asked if he has "confidence" in America's new commander in chief, the chairman of the Senate Armed Services Committee twice said: "I do not know."

"I do not know because has made so many comments that are contradictory," McCain told ABC's George Stephanopoulos.

"But I think the fact that he's appointed and nominated these outstanding individuals is bound to be an encouraging sign," he continued. "I trust them and have worked with them over many years."

McCain, a Republican, has been a leading critic of Rex Tillerson, Trump's pick for secretary of State. But he admitted Sunday that he is impressed with the generals Trump has appointed to his administration.

"I have the utmost confidence in Gen. Mattis, Gen. Kelly and Gen. Flynn," he said. "I couldn't have picked a better Cabinet."