Iranian Foreign Minister Javad Zarif says negotiations with the US to save the 2015 nuclear deal are pointless because US President Donald Trump is not trustworthy.

Speaking at the 4th edition of Mediterranean Dialogues (MED 2018) forum in the Italian capital of Rome, the Iranian top diplomat said Thursday that Tehran would not renege on any deal made.

Trump pulled out of the Joint Comprehensive Plan of Action (JCPOA) in May, branding the landmark agreement between Iran and the P5+1 group of countries – the US, the UK, France, China, Russia and Germany – a "disaster."

The American head of state pledged back then that he would bring back sanctions that were removed under the deal and impose tougher ones until the Islamic Republic agrees to renegotiate a deal that would further limit its nuclear program, ban developing certain ballistic missiles and roll back Tehran’s influence in the region.

Iran has made it clear that it continues to stick to the current terms of the deal and work with the European signatories to overcome the sanctions.

Zarif stressed that the US could not be trusted for any further talks without the required guarantees, something he said was too much to expect from the Trump administration.

"If we are to make an agreement with the United States, what is the guarantee that the agreement will last after the flight? You remember Canada?" he said, taking a jab at Trump for his last minute refusal to sign a G7 summit closing statement in June, after his plane left host Canada.

"How are we to be confident that the signature stays on the paper?" Zarif added.

The deal’s future became even more unclear earlier this month, after sweeping new American sanctions targeting Iran’s oil exports came into effect.

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Despite granting waivers to Iran’s main oil buyers for the time being, Washington has warned that it would punish European companies that engage in business deals with Iran.

Iran has threatened to pull out of the JCPOA if it no longer received the economic benefits of it.

Zarif said while he was certain that Europe would be able to guarantee the deal’s future, Iran was not going to wait long.

“As I said we rely on our people and that is where the red line is,” he said. “If our people believe that the deal is not conducive to their economic interests then we will have to respond to the will of our people.”

The agreement, reached after extensive talks in the Austrian capital of Vienna, envisaged the removal of all nuclear-related sanctions on Iran in exchange for limits on certain parts of the country’s nuclear energy program.

"We spent two-and-a-half years, this is not a two-page document, this is not a picture opportunity. This is a 150-page document," Zarif said of the JCPOA, suggesting that Trump's objection to deal was mainly because of his “hatred” for the things his predecessor, Barack Obama, had accomplished.

"Why should we resume another talk just because somebody doesn't like it, just because somebody hates his predecessor? That's not the reason you engage in diplomacy, diplomacy is a serious game and we are ready for a serious game," the FM said.

Zarif pointed out that the deal was not between Iran and the Obama administration because it also involved the P5+1 and the European Union (EU) while also being enshrined in UN Security Council Resolution 2231.

The remaining five signatories to the JCPOA have planned to support an EU push to establish a special payment system – called the Special Purpose Vehicle (SPV) – to continue trade and business ties with Iran.

However, some European companies have already pulled out of Iran for fear of US penalties.