WASHINGTON (AP) — A top GOP senator says President Donald Trump needs to understand that he's "misjudging" Russian leader Vladimir Putin.

Sen. Lindsey Graham says Trump's had a "bad week" when it comes to Russia in the wake of the Trump-Putin summit Monday in Helsinki.

Here's what the South Carolina lawmaker says about Trump: "I think it's imperative that he understand that he's misjudging Putin. I don't think he was prepared as well as he should have been."

Trump has come under heavy criticism since the Putin meeting, where he declined to challenge Putin on Russian interference in U.S. elections.

Graham says Trump is right to criticize previous American administrations for their handling of Russia. But he says Trump "is not making the problem better. He's making it worse."

He adds that Trump "has the potential to make it better, and I hope he will."