The Obama administration is focused on building enough support for the Iran deal to keep Congress from “spoiling” the agreement, the White House said on Wednesday.

“There are several indications that we are succeeding in our effort to build support in Congress,” White House spokesman Josh Earnest told reporters, according to the Reuters news agency.

Congress has until September 17 to reject or approve the deal that was signed between Iran and six world powers, including the United States, in July.

Supporters of the agreement have had the momentum growing in their favor. A 29th senator, Democrat Patty Murray of Washington, came out in favor of the deal on Tuesday.

So far, only two Senate Democrats — New York’s Chuck Schumer and New Jersey’s Bob Menendez — have announced that they will vote against the deal, though several key Democratic senators have yet to announce their position.

Earlier this week, the Iran deal also received the backing of Senate Minority Leader Harry Reid, who said it is the “best way” to curtail Iran’s military ambitions.

On Tuesday, Republican Bob Menendez, who chairs the Foreign Relations Committee and is a leading voice against the deal, acknowledged that the White House lobbying campaign for the Iran nuclear deal has generated results, and said he doesn’t know if opponents of the deal can prevail.