President Obama doubled down on remarks he made last week saying that the GOP was making "common cause" with the Iranian hardliners, saying his words were "absolutely true factually."

"The truth of the matter is, inside of Iran, the people most opposed to the deal are the Revolutionary Guard, the Quds Force, hardliners who are implacably opposed to any cooperation with the international community. And there's a reason for that, because they recognize that if, in fact, this deal gets done, that rather than them being in the driver's seat with respect to the Iranian economy, they are in a weaker position," the president said in an interview with CNN that aired Sunday.

The comparison, which Mr. Obama made during a speech defending the Iran nuclear deal last week, has got an angry response from some of the deal's opponents who said he had crossed a line. Senate Majority Leader Mitch McConnell, R-Kentucky, said the president was treating the issue "like a political campaign."

"Demonize your opponents, gin up the base, get Democrats all angry and, you know, rally around the president. To me, it's a different kind of issue," the majority leader said at a news conference last week.

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Mr. Obama said in the CNN interview that McConnell and other Republicans "jumped out and opposed [the deal] before they even read it." He argued that the deal cuts off Iran's pathway to a nuclear weapon and sets up the most comprehensive inspections regime ever, and the near-universal opposition among Republicans "is reflective of a ideological commitment not to get a deal done."

Given the stiff opposition from Republicans, Mr. Obama is working to shore up enough Democratic support to ensure that there is not enough votes in Congress to override his veto when lawmakers issue a resolution disapproving of the deal. House Republicans said last week they have the necessary votes to disapprove of the deal.

The interview was taped last Thursday just before Chuck Schumer, the influential Democratic senator from New York, announced he would vote against the deal.

Mr. Obama also ducked a question about whether he was concerned about confronting the strong possibility that he might have to use military force against Iran if the deal fails.

"I have a general policy on big issues like this not to anticipate failure. And I'm not going to anticipate failure now because I think we have the better argument," he said.

The president has not pledged to use military force against Iran if the deal falls apart but has said it is still an option if Iran tries to cheat on the agreement or begins trying to build a nuclear weapon after certain provisions in the deal expire in 10 to 15 years.

"We haven't given away any of our military capabilities. We're not in a weaker position to respond," Mr. Obama said at a press conference about the deal last month.

Defense Secretary Ashton Carter also said in July, "One of the reasons this deal is a good one is that it does nothing to prevent the military option - the U.S. military option."