Donald Trump's campaign chairman, Paul Manafort, on Sunday defended the GOP nominee's comments about Muslim lawyer Khizr Khan, saying the loss of Khan's son "isn't the issue" and that the real focus should be on "radical Islamic jihad."

"Mr. Trump and all of us give him our sympathy and empathy for the loss of his son. I mean, that was a real tragedy," Manafort said on CBS' "Face the Nation" Sunday. "The issue is not Mr. Khan and Donald Trump, the issue really is radical Islamic jihad and the risk to the American homeland. That's the issue."

Khan, whose son Army Capt. Humayun Khan was killed in Iraq in 2004, spoke at the Democratic convention Thursday, delivering one of the most powerful moments of the convention. Asked about the speech in an interview with ABC News, Trump came under fire Saturday for his response to Khan's suggestion that he has "sacrificed nothing and no one."

In response, Trump said that he has in fact suffered: "I think I've made a lot of sacrifices," he said. "I work very, very hard."

Manafort repeatedly dodged questions about why Trump focused on Khan's wife-- "I'd like to hear his wife say something," Trump said -- by suggesting moderator John Dickerson's questions were "Clinton talking points."

"Mr. Trump was asked about Mr. Khan, he didn't raise Mr. Khan," Manafort said, asked again about why Trump responded the way he did.

Responding to questions about Trump's participation in all three presidential debates this fall, Manafort suggested the Clinton campaign was conspiring to ensure low viewership and that Trump is looking for "maximum audience participation." Trump tweeted Friday that Clinton and the Democratic Party "are trying to rig the debates so 2 are up against major NFL games." (The dates and venues for presidential debates are set by an independent commission, not either party.)

"He said he wants to participate in it but just like we discovered in the hack of the DNC, Mrs. Clinton likes low audiences watching her debates, that's what she conspired for to keep Bernie Sanders from getting a large audience," he said.

Manafort said the Trump campaign would be sitting down with the Commission on Presidential Debates to discuss the issue and make sure "there's a broad audience watching the debates."

As for concerns about Trump's ties to Russia and his past praise for Russian President Vladimir Putin, Manafort said Russia is a "threat" but refused to echo the strong criticism of the country issued by House Speaker Paul Ryan and others in the GOP.

"I think Mr. Trump has said on the campaign trail the biggest threat is failed leadership on the part of Obama and Clinton," he said. "As far as Russia or China or Syria or ISIS, they're all threats and he has said he will have a robust policy that will put America's interests first."