Paul Ryan. Jeff Swensen/Getty Images Paul Ryan on Friday ripped the "alt-right" platform, on which he accused his primary opponent of running, after his challenger questioned why the US has "Muslims in the country."

The House speaker told Wisconsin radio host Charlie Sykes that the comments about Muslims made by his opponent, Wisconsin businessman Paul Nehlen, were "dark, grim," and "indefensible."

Ryan later said the alt-right, a group that has provided some of the most fervent support of Republican presidential nominee Donald Trump, "isn't even conservatism."

"Look, I hate to even give such comments currency by even talking about them," Ryan said. "This is not the US Constitution. This is not the US Bill of Rights. Let's just be really clear about this."

"I think they call it alt-conservatism," he added, before Sykes jumped in and referred to it as the alt-right.

"This is not Wisconsin conservatism ... That kind of dark, grim, indefensible comments are going to be clearly rejected and repudiated on Tuesday. I have a hard time seeing the thinking behind this. Unfortunately, we see some of it these days."

Sykes asked Ryan what he'd say if Trump were to support Nehlen's comments, which Nehlen said on a Chicago radio station on Thursday.

"I'm not going to go into the hypothetical," Ryan said, repeating that his endorsement of Trump is not a "blank check."

He acknowledged, though, that there could be a point at which he withdraws his endorsement of Trump. But he declined to say what might make him rescind his support.

"If I hear things that I think distort conservatism, that disfigure our values ... I'm going to defend ourselves so people in this country don't get a misperception about who we are and what we believe in," he said. "I've had to do that from time to time, certainly more than I've wanted to."

He mentioned his defense of the parents of a slain Muslim US soldier, with whom Trump started a feud after the soldier's father denounced him at the Democratic National Convention.

The Wisconsin Republican added that he has "no plans" to speak with Trump this week and that he has "not spoken to him since the convention" last month.