A general view of streets in Tehran, Iran on the first anniversary of nuclear deal between Iran and world powers on January 16, 2017.

The Iran nuclear deal is on life support and on a trajectory for collapse, many policy experts believe, despite U.S. President Donald Trump's current continuation of sanctions relief.

Trump agreed to waive sanctions on the Islamic Republic in mid-January as part of the 2015 nuclear pact, but pledged that this time it was the country's "last chance", threatening a U.S. walkout.

"I am very concerned that it will not survive May 2018. Mr. Trump has set an unreasonable list of demands out that I do not think any realistic European or Congressional agreement could satisfy," Richard Nephew, program director at the Center on Global Energy Policy at Columbia University, told CNBC. Nephew served as the lead sanctions expert for the U.S. State Department negotiating with Iran from 2013 to 2014.

The Joint Comprehensive Plan of Action (JCPOA), signed by all five United Nations Security Council members and Germany in 2015, allowed the lifting of international sanctions on Iran in exchange for compliance with restrictions on its nuclear program. The U.S. president is required to recertify it every 90 days or leave its fate to Congress.

While the International Atomic Energy Agency (IAEA) has verified Iran's compliance, Trump continues to deride the agreement, calling for more sanctions on the Islamic Republic particularly for its ballistic missile program and human rights abuses, which were not part of the JCPOA. Trump announced on January 12 that if Congress and the deal's European signatories did not fix the deal's "disastrous flaws", the U.S. would withdraw.

"The simple reality is that Trump hates the JCPOA even as he doesn't understand it," Nephew said. "And though his advisors are attempting to get him to think about it more pragmatically, their perennial struggles don't auger well for its survival."