Several senior Republicans have condemned Donald Trump after he mounted a defence of "killer" Vladimir Putin and publicly attacked judges who blocked his "Muslim travel ban".
In an interview with Fox News broadcast before the Super Bowl, Mr Trump suggested he thinks the US and Russia are morally equivalent.
When asked by host Bill O'Reilly if he respects Mr Putin, Mr Trump replied: "I do respect him."
He said he thought it was better to get along with Russia because they could help in the fight against Isis.
But "Putin's a killer," Mr O'Reilly said.
Mr Trump replied: "There are a lot of killers. We've got a lot of killers.
"What do you think, our country's so innocent?"
His comments were quickly attacked by Republicans.
"He's a thug," Senata majority leader Mitch McConnell told CNN's State of the Union. "The Russians annexed Crimea, invaded Ukraine and messed around in our elections.
"No, I don't think there's any equivalency between the way Russians conduct themselves and the way the United States does."
Senator Mark Rubio tweeted: "When has a Democrat political activists [sic] been poisoned by the GOP, or vice versa? We are not the same as Putin."
He added: "Only reason we should ever lift sanctions on Putin is if he meets conditions of sanctions and ends violations of Ukraine sovereignty."
Representative Liz Cheney tweeted to say Mr Trump's statement was "deeply troubling and wrong."
However, Vice President Mike Pence defended the president on NBC's Meet the Press.
When asked whether Mr Trump was creating a "moral equivalency" between the US and Russia, he replied: "No, not in the least.
“President Trump has been willing to be critical of our country’s actions in the past."
Mr Pence added: "But what you’re hearing there is a determination by the president of the United States to not let semantics or the arguments of the past get in the way of exploring the ability to work together with Russia and with President Putin in the days ahead.”
When asked to elaborate about his respect for Mr Putin in his interview with Fox News, Mr Trump said: "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."
On Sunday, Mr Trump criticised the federal judge who halted his executive order that temporarily banned travel and immigration from seven predominantly Muslim countries.
The signing of the order more than a week ago resulted in global confusion as hundreds of travellers and visa-holding immigrants were detained in airports across the US. It sparked massive protests and several lawsuits against the Trump administration.
"Just cannot believe a judge would put our country in such peril," he wrote, tweeting from his Mar-a-Lago resort in Florida. "If something happens blame him and court system. People pouring in. Bad!"
He added that the courts were making the Department of Homeland Security's job "very difficult".
It follows a similar attack against another judge, James Robart, who initially blocked the executive order.
Mr Trump's outburst against the judiciary have brought a stinging rebuke from Mitch McConnell, the Senate majority leader.
'I think it is best not to single out judges for criticism,' he told CNN's Jake Tapper on State of the Union. 'We all get disappointed from time to time at the outcome in courts on things that we care about. But I think it is best to avoid criticising judges individually.'
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