Washington, September 3 (RHC)-- Republican presidential hopeful Marco Rubio says that if he becomes the next U.S. president, he will strike down the Iran nuclear agreement and reimpose sanctions against the Islamic Republic on his first day in the White House.

In an interview with Fox News on Wednesday, Rubio said the nuclear accord with Iran can be undone by the next U.S. president. "This is not a treaty, there's nothing about this that's binding on the next administration."

"When I'm president of the United States, we will reimpose those sanctions on Day 1, and then I will go to Congress, ask them even to increase sanctions more, and I will back that up with a credible threat of military force," Rubio said.

Republicans, who control both houses of Congress, almost unanimously oppose the agreement because they say it gives too many concessions to Iran and threatens the security of Israel, a major US ally in the Middle East.

Congress is reviewing the nuclear agreement and has until September 17 to vote to either approve or disapprove of it. U.S. President Barack Obama has said he is confident that the nuclear accord will go forward despite opposition from congressional Republicans.

On Wednesday, momentum shifted in favor of the nuclear accord, with Democratic Senator Barbara Mikulski becoming the 32nd Senate Democrat, along with two independents, to announce that she would support the deal.

Democrats need 34 votes in the Senate, or 146 in the House of Representatives, to sustain the veto President Obama has promised. Mikulski's announcement means Democrats will now have enough votes to protect the nuclear agreement in Congress.

Analysts say Republican presidential candidates are opposing the nuclear agreement to avoid angering the pro-Israel lobby and preventing their Democratic rivals from getting any political advantage by resolving the Iranian nuclear issue.