The lobbying in the American Congress for and against the international deal over Iran’s nuclear programme is getting more intense as a September 17 deadline for Congress to act on the deal gets closer. A Republican bill has been tabled that calls for the deal to be scrapped and Republican majorities in the House and Senate are expected to back the bill, which would force US President Barack Obama to use his presidential veto on the rejectionist bill. A presidential veto can be overruled by two thirds of the Senate, so it is good news for the Obama administration that a 34th senator has agreed to support the Iran deal, which means that a presidential veto will be sustained and the deal can go ahead.

But this slim margin is not enough to allow anyone in the administration to sleep easy so they will be looking for a lot more support over the next few days. And Secretary of State John Kerry has made clear that the administration wants the rejectionist bill to fail at the first round of voting, so that this major foreign policy initiative can get a more resounding level of Congressional support that will indicate to the world that the American president has some authority.

The danger of Congress dismissing the deal is that it would put the US into unilateral isolation because the deal is not just a bilateral US-Iran agreement, but also includes China, Russia, Britain, France and Germany who will take it to the UN Security Council and go ahead, with or without the US.