Washington: The Senate begins debate on Tuesday over legislation empowering Congress to review and possibly reject any nuclear pact the Obama administration develops with Iran.

The bill approved by the Senate Foreign Relations Committee has gained the tacit approval of Obama, and proponents are trying to discourage any changes. They recognise that politically driven amendments could undermine Democratic support and sink the carefully crafted measure.

The legislation would block Obama from waiving congressional sanctions for at least 30 days while lawmakers weigh in. And it would stipulate that if senators disapprove the deal, Obama would lose authority to waive certain economic penalties — an event that would certainly prompt a presidential veto.

Among proposed additions to the bill are demands that Iran release any US citizens it is holding and refrain from any cooperation with nuclear-armed North Korea. Another insists that any agreement be treated as an international treaty, requiring two-thirds ratification by the Senate.

Another set of amendments would block any sanctions relief for Iran until it meets goals the US set years ago as negotiating stances and has long since abandoned.

Meanwhile, Republican presidential candidates are lining up to oppose any deal with a government the US considers the world’s leading state sponsor of terrorism and to show their support for the Israeli regime.

Senator Marco Rubio of Florida wants to require Iran’s leaders to publicly accept Israel’s right to exist, a nearly impossible mandate. Senator Ted Cruz of Texas hopes to put the onus on advocates to win congressional approval of a deal, and not on opponents to gather enough votes for rejection.