U.S. Sen. Mazie Hirono says she will support the agreement negotiated with Iran by President Barack Obama’s administration and other world powers to try to block Iran’s progress in developing a nuclear weapon.

“After careful consideration, particularly weighing the risks involved in Congress approving or rejecting the deal, I have concluded that supporting this agreement means that Iran’s nuclear weapons program, which was on the verge of success, will be disabled for many years,” Hirono said in a prepared statement released Monday.

Hirono, D-Hawaii, pointed out the agreement includes a pledge by Iran that under no circumstances will it seek to develop or acquire a nuclear weapon. The agreement “will enable the U.S. and the international community to take appropriate action, including military action, should Iran violate this unequivocal pledge,” she said.

Obama warned earlier this month the only alternative to the Iran agreement is “some form of war,” but the deal faces strong opposition from Republicans in both the House and Senate. It is also opposed by Israeli Prime Minister Benjamin Netanyahu.

Congress is expected to consider a Republican-sponsored resolution in September disapproving the Iran deal. If such a resolution passes in the House and Senate as expected, Obama is expected to counter by vetoing it. Opponents of the Iran deal would then need to muster a two-thirds majority in both the House and Senate to override that veto and block the agreement.

That veto override looks increasingly unlikely, with a growing number of House and Senate Democrats including Hirono and Sen. Brian Schatz, D-Hawaii, announcing they support the Iran agreement.

Obama needs 34 votes in the Senate or 145 votes in the House of Representatives to sustain a veto. Vote count estimates by national news organizations suggest the president is close to the count he needs in the Senate, and may also be able to gather enough votes in the House.

Hirono said the agreement will require Iran to give up its capacity to develop nuclear weapons. However, if the deal is rejected by Congress, Hirono said other world powers including China, the United Kingdom and Russia will abandon the negotiations.

“This agreement is the best option to halt Iran’s nuclear weapon program,” she said. “At the same time, this deal does not solve all the concerns we have about Iran’s activities, particularly Iran’s support for terrorism. I will support increased efforts, along with our allies, to counter Iran’s destabilizing and malign actions within and outside the Middle East.”