Washington: President Barack Obama again warned the Republican controlled Congress that he would veto any move to derail the landmark Iran nuclear deal, but with several more senators backing it, he may not have to wield his pen.

The deal between Iran and six world powers led by the US has now gained the support of 42 senators – enough to bottle up a resolution of disapproval in the 100 member senate with a filibuster and spare Obama the need to overturn it.

White House, press secretary Josh Earnest said the administration felt

“gratified” by the growing support for the Iran nuclear deal He suggested that the White House expects Democratic supporters to filibuster the vote to disapprove the accord.

Supporters “should take the necessary steps in Congress to prevent Congress from undermining the agreement,” Earnest said.

Even as Obama stood on the brink of a legacy defining foreign policy victory, opponents kept up their tirade against the deal with former Vice President Dick Cheney denouncing it as “madness” and “shameful”.

Calling it a “capitulation” by world powers, he said it “strengthens our adversaries, threatens our allies and puts our own security at risk.”

Meanwhile, the White House warned the Congress as it returned from its summer recess that the enactment of a joint “resolution would greatly undermine our national security interests on multiple fronts.”

It would also “deal a devastating blow to America’s credibility as a leader of diplomacy and could ultimately result in the exhaustion of alternatives to military action.”

In selling the deal to the lawmakers, the Obama administration has time and again invoked the support of India saying countries which have paid a hefty economic price would not back the sanctions again if the deal was killed by the Congress.

The new warning came even as four more senators joined the supporters of the deal, taking their number to 42, all of them Democrats or independents who caucus with Democrats.

Announcements in support of the deal Tuesday came from senators Richard Blumenthal, Maria Cantwell, Gary Peters and Ron Wyden, ensuring that the Republicans would not have the 60 votes necessary to close debate on the disapproval resolution.

But Senator Joe Manchin III Tuesday became the fifth Democrat to announce he would vote to disapprove of the deal.

Also Tuesday, the last undecided Senate Republican, Susan Collins, announced her opposition, dashing any White House hopes for bipartisan support.

Faced with the prospect of a filibuster, Republican Majority Leader Mitch McConnell said the Democrats “should not hide behind procedural obfuscation to shield the president or our individual views.

He argued that the Iran disapproval should be decided on a majority vote for final passage, not on a procedural vote requiring 60 senators.

But Democratic Minority Leader Harry Reid cited multiple occasions where McConnell threw up procedural roadblocks when Republicans were in the minority.

Lawmakers have until Sep 17 to weigh in for or against the agreement, when the 60 day review period expires.

Meanwhile, Cheney speaking at the American Enterprise Institute conservative think-tank in Washington Tuesday, blasted the deal saying it will see the “arming and funding (of) Iran while simultaneously providing them a pathway to a nuclear arsenal.”

It “is not an act of peace, is not – as the president claims – the only alternative to war. It’s madness,” Cheney added.