How will the US decision to "decertify"the Iran nuclear deal affect the parties involved in the deal? Discuss.

Iran nuclear deal was struck between Iran and six world powers – the US, UK, Russia, France, China, and Germany in 2015 which lifted crippling economic sanctions on Iran in return for limitations to the country’s nuclear energy programme.
US President has decertified the nuclear deal which implies that it is for Congress to either impose the sanctions on Iran or maintain the status quo.

• Decertification of the deal, does not put US in violation of the deal as it does not re-impose the sanctions.
• The issue gives Congress a 60-day window to reimpose Iran sanctions suspended by the deal using a special, extremely fast process.
• Decertification corrodes the legitimacy of the deal.
• European allies fear that this move towards the agreement could prompt Iran to resume its nuclear weapons program.
• Any such unilateral changes to the agreement are likely to trigger the deal’s collapse and a return to a nuclear standoff in the Middle East.
• This could raise the risk for India as it has stepped its engagement with Iran and put a brake on Chabahar Port, INSTC etc. where huge investments have been made.
• Withdrawal of the deal could make the situation in middle east more volatile.

Decertification does not formally end the Iran deal  but it creates serious threats to its continued existence.