NEW YORK (JTA) — Three more U.S. senators have thrown their support behind the Iran deal, bringing President Barack Obama to within four votes of blocking a congressional vote of disapproval on the nuclear agreement.

The three additional senators were Cory Booker of New Jersey, Mark Warner of Virginia and Heidi Heitkamp of North Dakota. All are Democrats.

Obama already has enough votes in the Senate to sustain a presidential veto of any congressional disapproval of the nuclear agreement. With four more votes of support, Senate Democrats would have the 41 senators necessary to filibuster and thereby block a disapproval resolution from even coming to a vote.

So far, only two Senate Democrats have come out against the deal: Chuck Schumer of New York and Robert Menendez of New Jersey. All the Senate’s Republicans are against the deal.

The nuclear deal reached July 14 will provide Iran with relief from certain sanctions in exchange for limits on Iran’s nuclear program.