THE US Senate voted on Thursday to block an attempt to derail the landmark Iran nuclear deal.

Democratic Party senators rallied round President Barack Obama to thwart opposition Republican attempts to force the White House to reject the agreement.

The resolution died with a whimper after a procedural motion to move the issue to a final vote, which needed the support of 60 out of 100 senators, failed to pass by 58 to 42.

Mr Obama welcomed the result, saying: “This vote is a victory for diplomacy, for American national security and for the safety and security of the world.

“I am heartened that so many senators judged this deal on the merits and am gratified by the strong support of lawmakers and citizens alike.”

The deal, hammered out this summer in Switzerland and Austria, lifts sanctions on Iran and recognises its right to peaceful atomic energy generation in return for UN inspections to ensure that it is not developing nuclear weapons.

With Congressional opposition to the agreement dead, Republicans nevertheless vowed to fight on in the House of Representatives, the lower chamber of Congress.

Republican legislator Blake Farenthold told the House of Representatives that his party would now “use the judicial branch of the government” to block the deal.

“What part of ‘Death to America’ do you not understand?” he asked, repeating the popular Iranian slogan.

Republican House of Representatives Speaker John Boehner warned: “This debate is far from over. We’ll use every tool at our disposal to stop, slow and delay this agreement.”