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Two more Democratic senators announced on Wednesday night that they would back the nuclear deal with Iran.

Senator Ed Markey, a Massachusetts Democrat, said on Wednesday he would support the deal, explaining in a statement that he believed "that if strictly implemented, this plan can be effective," according to Reuters.

He was followed by Senator Joe Donnelly from Indiana, who threw his support behind the Iran nuclear deal as well, saying that the United States must exhaust every option before going to war with Iran.

"Despite having questions about Iran’s intentions, I am willing to give this agreement the opportunity to succeed," he said in a statement quoted by The Hill.

"While I share the concerns expressed by the agreement’s critics about what may happen 10, 15, or 20 years from now, I cannot in good conscience take action that would shift the potential risks of 2026 and 2031 to 2016," added Donnelly.

He said that while "the day may come when we are left with no alternative but to take military action to prevent Iran from crossing the nuclear threshold. Taking that path would be a difficult and costly choice. ... I owe it to the men and women of our Armed Forces and to the people of Indiana to have exhausted every other option to stop Iran before we would consider putting any of our service members in harm’s way."

Congress has until September 17 to vote on the deal. If all Senate Republicans oppose it, 13 Democrats will also be required to override a presidential veto.

So far, just two Democrats have announced they would vote against the deal - Chuck Schumer of New York and Robert Menendez of New Jersey, who announced his decision to vote against the deal on Tuesday.

Senate Minority Leader Harry Reid (D-NV) has been holding off on announcing his stance on the deal, after indicating he intends to talk with influential Jewish backers before deciding.

Reid is among seven Democrat senators listed by The Hill as "leaning" toward supporting the Iran deal, but it is possible that in talks with the prominent Jewish backers he could be convinced to oppose the deal, a move which would have great impact given his prominent position.