“The option of getting back to the negotiating table is close to zero if (US) Congress votes down the nuclear deal,” said Philipp Ackermann, Berlin’s second-ranking diplomat in Washington, Politico reported.

He further described the sabotage of the accord by the Congress as a “nightmare” and a “catastrophe”.

“That (derailment of the nuclear agreement) would undermine international negotiations in general and damage the credibility of future agreements struck by diplomats. It would be a nightmare … a catastrophe," he added.

Iran and the Group 5+1 (Russia, China, the US, Britain, France and Germany) on July 14 reached a conclusion on a lasting nuclear agreement that would terminate all sanctions imposed on Tehran over its nuclear energy program after coming into force.

The 159-page deal has its own opponents and proponents both in Iran and the other countries that are parties to the JCPOA, particularly the US.
While the United Nations Security Council has adopted a resolution to endorse the deal, the text of the document needs to be ratified by both Iran's Parliament and the US Congress.