Senate Majority Leader Mitch McConnell is warning Republicans considering challenging President Donald Trump in 2020 that it would be “a waste of time.”

The Kentucky Republican told The Associated Press in an interview Wednesday that that it would be “very, very difficult to unseat the president in the primary.”

Republicans, such as retiring Sen. Jeff Flake of Arizona, are considering challenging Trump in 2020.

McConnell said that “would be a waste of time frankly. But the people who would be likely to challenge the president would not be coming to me for advice.”