The White House refused Thursday to back down on comparisons President Obama drew a day earlier between Republicans and Iranian hardliners.

When asked at the daily press briefing if Obama would retract his statement, White House Press Secretary Josh Earnest said no.

During a speech at American University in Washington on Wednesday, Obama went after critics of the deal, who he said were “selling a fantasy” to the American people.

He added that Iranian hardliners chanting "Death to America" don't represent all of Iran.

"In fact, it's those hardliners who are most comfortable with the status quo," Obama said. "It's those hardliners chanting 'Death to America' who have been most opposed to the deal. They're making common cause with the Republican caucus."

Following his remarks, Senate Majority Leader Mitch McConnell demanded Obama retract the statement. McConnell, R-Ky., called the comments “bizarre and preposterous” in a statement released Wednesday afternoon, adding that “supporters and defenders” of the proposed deal should reject the president’s “offensive rhetoric.”

“Members of both parties have serious and heartfelt concerns about the Iran deal,” he said in a statement. “These Democrats and Republicans deserved serious answers today, not some outrageous attempt to equate their search for answers with supporting chants of 'Death to America.'”

Sen. Kelly Ayotte, R-N.H., also blasted the president for the remarks.

"I think it's beneath that office to be able to make these analogies," she told Fox News.

The president's remarks were part of an intense lobbying campaign by the White House ahead of Congress' vote next month to either approve or disapprove the international agreement. Opponents of the agreement have streamed to Capitol Hill  to make their case, and have spent tens of millions of dollars on advertisements.

The White House is preparing for the likelihood that lawmakers will vote against the deal next month and is focusing its lobbying efforts on getting enough Democrats to sustain a presidential veto. Only one chamber of Congress is needed to sustain a veto and keep the deal in place.

Obama needs 146 Democrats in the House or 34 in the Senate to sustain a veto. As of Wednesday afternoon, 16 House Democrats and 11 senators had publicly declared their support for the deal.

The White House has said it is confident it can sustain a veto at least in the House.

The Associated Press contributed to this report.