Donald Trump insists he "respects" Russia's Vladimir Putin even though he is "a killer".

Promotions for a sensational interview with Donald Trump and Fox News’ Bill O’Reilly shows the US President defending the murderous reputation of the Russian President, Vladimir Putin.

Due to air in the hours before the wildly popular Super Bowl, Trump admits he ‘respects’ the leader many others have been wary of.

In the O’Reilly Factor snippet, the two interchange comments about the ultra-conservative leader being “a killer”.

O’Reilly: Do you respect Putin?

Trump: I do respect him, but …

O’Reilly: Do you? Why?

Trump: Well I respect a lot of people but that doesn’t mean I’m going to get along with him. He’s a leader of his country. I say it’s better to get along with Russia than not. And if Russia helps us in the fight against ISIS, which is a major fight, and Islamic terrorism all over the world — that’s a good thing. Will I get along with him? I have no idea.

O’Reilly: But he’s a killer though. Putin’s a killer.

Trump: There are a lot of killers. We’ve got a lot of killers. What do you think? Our country’s so innocent?

The conversation was released after news broke that Vladimir Kara-Murza, a major critic of the Russian President, has been hospitalised for unexplained “multiple organ failure”.

The political journalist, who advocates for free and open elections, has previously claimed he was suspiciously poisoned in 2015.

In a statement, Kara-Murza’s lawyer said: “None of the medical staff can explain the reason for his current condition. Both last time and once again now.”

Alexander Litvinenko, a high-profile defecting Russian spy, died from radiation poisoning in 2006.

Trump’s appraising comments come after Putin effectively endorsed his White House bid last year, telling reporters in Moscow that the supposed real estate billionaire is “unquestionably talented.”