The Iran nuclear agreement gained the backing of three more senators — Cory Booker of New Jersey, Mark Warner of Virginia and Heidi Heitkamp of North Dakota.

The latest announcements on Thursday boosted supporters' hope they can block a disapproval resolution in the Senate and spare President Barack Obama from resorting to a veto.

Heitkamp said the deal is the best chance to prevent Iran from acquiring a nuclear weapon and keep America safe.

Supporters are aiming to collect 41 votes in favor, which would allow them to block a final vote on the disapproval resolution in the Senate and save Obama from exercising his veto power.

Heitkamp raised the number of backers to 37.