US President Barack Obama has secured the necessary number of votes in Congress to ensure the passage of the Iran nuclear deal.
Democratic Senator Barbara Mikulski of Maryland became the 34th senator to declare her support Wednesday, saying that in her view the deal was the best way to prevent Iran obtaining nuclear weapons.
Her announcement came just one day after Senators Chris Coons (D-DE) and Bob Casey (D-PA) similarly declared their support, providing the White House with 33 out of the 34 votes it would need to maintain a presidential veto.
Obama will be using that veto if - as appears likely - the Republican-dominated Congress rejects the Iran deal by a simple majority.
The only way for Congress to override that veto would be via a two-thirds majority vote in both houses, which would require the support of a sizable number of Democrats as well. With 34 Senators in favor of the deal, however, such a majority is now impossible.
Mikulski said Wednesday that while the deal is not perfect, "I have concluded that this Joint Comprehensive Plan of Action is the best option available to block Iran from having a nuclear bomb."
She added that while she will vote for the deal, "Congress must also reaffirm our commitment to the safety and security of Israel."
Republicans are unified in their opposition to the Iran accord.
Two top Democratic senators - Chuck Schumer and Robert Menendez - are also opposed, as are a handful of Democrats in the House, including Steve Israel, the chamber's highest-ranking Jewish member.
But that will not be enough to grant victory to the nuclear deal's opponents, who argue it gifts Iran with all its key demands without actually ensuring it will not obtain nuclear weapons at a later date.