"Late Night"/screenshot
Former Secretary of State Hillary Clinton with "Late Night" host Seth Meyers.
"I want to ask you a couple questions about Donald Trump. First question: Have you heard about him?" Meyers joked to Clinton.
"I have to say Seth, I no longer think he's funny," she replied.
"I will say I started feeling that way," Meyers agreed.
Trump, the Republican presidential front-runner, sparked intense backlash earlier this week when he proposed temporarily stopping virtually all Muslims from entering the US, including immigrants and tourists.
The billionaire businessman argues that his hard-line approach is necessary to protect the US from terrorism until the "hatred" in the Muslim community is contained. But a wide range of critics, including Clinton, called the proposal offensive.
"I think for weeks, you and everybody else were just bringing folks to hysterical laughter and all of that," Clinton told Meyers. "But now he's gone way over the line. And what he's saying now is not only shameful and wrong, it's dangerous."
Clinton, the Democratic presidential front-runner, said that Trump's proposal is giving terrorist groups a recruiting tool to frame their fight as a broader religious war.
"This latest demand that we not let Muslims into our country really plays into the hands of the terrorists. And I don't say that lightly, but it does," she said. "He is giving them a great propaganda tool: a way to recruit more folks from Europe and the United States. And because it's kind of crossed that line, I think everybody - and especially other Republicans - need to stand up and really say, 'Enough.'"
A wide range of Republicans, including presidential candidates and party leaders, have criticized Trump's proposal in sharp language. Others have simply said that they disagree with the policy idea. Polls have found that Republican voters are supportive of Trump's plan.