Obama secures key backing at Congress

US President Barack Obama on Wednesday earned sufficient congressional backing to ensure the Iran nuclear deal does not get blocked, when a veteran Democrat became the crucial 34th senator to back the controversial accord.

Most US lawmakers are opposed to the deal, which would ease punishing economic sanctions on Tehran while preventing it from advancing its nuclear program. Many Republicans warn that the Islamic republic will seek to cheat its way to an atomic bomb.

But with Senate Democrat Barbara Mikulski announcing her support Wednesday, the deal now has 34 backers in the 100-member Senate -- the magic number needed to uphold a certain Obama veto should Congress pass a resolution that disapproves of the deal.

A vote in the House of Representatives is now set for next week. Overcoming a veto requires a two-thirds vote in the Senate and House.

Some Republicans have urged walking away from the deal and renegotiating tougher terms with Tehran. But US negotiators have warned that such a move could see the fragile international coalition that secured the agreement fall apart.

Republicans are unified in their opposition, warning that the deal leaves a civilian nuclear program intact, and that sanctions will provide Iran with a windfall of up to $150 billion, which they say could be funnelled toward terrorist operations.

Having been assured that the deal will survive, the White House is now eyeing another key threshold. If it gains backing from seven of the remaining undecided Senate Democrats to boost its numbers to 41, it could prevent Republicans from reaching the 60 members needed to force a vote on the resolution of disapproval. That would save Obama the embarrassing step of cobbling together a minority coalition to sustain his veto preserving his landmark agreement, a process that would sow doubts among a skeptical American public and Washington's international partners, which are keen to see strong US commitment to the accord.