Iran's Supreme Leader, Ayatollah Ali Khamenei, threatened on Tuesday to "set fire" to the nuclear deal sealed with world powers if US presidential candidates reneged on the agreement.

Presumptive Republican candidate Donald Trump said last August it would be hard to "rip up" the deal, but if elected president he would "police that contract so tough they don't have a chance".

Iran can expect a shift in relations with the United States to a more aggressive posture under a Republic president, a reversal of the warming trend nurtured by Democratic President Barack Obama.

"The Islamic Republic won't be the first to violate the nuclear deal. Staying faithful to a promise is a Koranic order," Khamenei said, according to state media. "But if the threat from the American presidential candidates to tear up the deal becomes operational then the Islamic Republic will set fire to the deal."

He did not identify any candidate and said he did not see a difference between Democrats and Republicans in the comments that state media said he made in a meeting with senior officials including President Hassan Rouhani, who championed the agreement.

Hillary Clinton, who Obama has endorsed to succeed him in the Nov. 8 election, said in March in a speech to a pro-Israel lobby group in Washington that Iran still posed a threat to Israel and needed to be closely watched.

She was secretary of state under Obama during his first term.

The United States and Europe lifted sanctions on Tehran in January under the deal that curbed Iran's nuclear programme. However, some restrictions remain, including on financial transactions, slowing Iranian hopes to reintegrate with world markets.

Khamenei noted that sanctions had not been completely lifted, issues with Iranian banks had not been resolved and that Iranian money that was being kept in other countries had not been returned.

"The nuclear deal has holes which, if they were closed, would reduce or cancel its disadvantages," he said.

He added: "Some think that we can get along with the Americans and solve our problems. This is an incorrect idea and a delusion."

The Supreme Leader also told the officials, who had gathered for a meeting to commemorate the holy month of Ramadan, that the issue of insurance for oil tankers had not been resolved.

Khamenei said Iran had met its obligations by halting the enrichment of uranium at 20 percent and shutting down nuclear facilities in Fordow and Arak.

Earlier, Iran's foreign minister, Mohammad Javad Zarif, urged the United States to do more to encourage banks to do business with Iran. – Reuters