Zarif, who is currently on an official visit to Pakistan, made the remark in a post on his official Twitter account on Tuesday after speaking to Geo News anchorperson Hamid Mir on 'Capital Talk'.
"[US President] Mr [Donald] Trump has made habit of being unpredictable and thus unreliable for anybody to engage with," the Iranian foreign minister said.
"Nobody will be interested in reaching any agreement with the White House if US signature only good for 4-8 yrs," he added.
Iran and the five permanent members of the United Nations Security Council – the US, France, Britain, Russia and China – plus Germany signed the nuclear agreement on July 14, 2015 and started implementing it on January 16, 2016.
Under the JCPOA, Iran undertook to put limits on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against Tehran.
Trump has repeatedly described the JCPOA, which was negotiated under his predecessor, Barack Obama, as “the worst and most one-sided transaction Washington has ever entered into,” a characterization he often used during his presidential campaign, and threatened to tear it up.
Trump on January 12 reluctantly agreed to waive sanctions against Iran that were lifted as part of the landmark deal, but said it would be the last time he issued such a waiver unless conditions were met.
The US president said he wanted America's European allies to use the 120-day period before sanctions relief again came up for renewal to agree to tougher measures and new conditions, otherwise Washington would pull out of the deal.
Trump signed an executive order on Monday, continuing a national emergency with respect to Iran first announced by former US President Bill Clinton in 1995.
He extended sanctions against Iran for another year, claiming that the Islamic Republic continues to pose “an unusual and extraordinary” threat to America.
In his latest report on March 5, Director General of the International Atomic Energy Agency (IAEA) Yukiya Amano once again confirmed Iran's compliance with the nuclear agreement, warning that any collapse of the deal would be a "great loss.
"As of today, I can state that Iran is implementing its nuclear-related commitments…If the JCPOA were to fail, it would be a great loss for nuclear verification and for multilateralism," Amano added.
Earlier in February, Zarif rejected as "improper" the conditions set by the United States for upholding the multilateral nuclear agreement, urging Washington to immediately fulfill its commitments under the deal.
He said, "A party to a multilateral agreement cannot set conditions for the deal. They [the Americans] have previously set some conditions that were improper. Their new conditions are improper as well."