President Hassan Rouhani on Tuesday said the world "praises" Iran over its standoff with Washington, and that the US had broken promises by abandoning a landmark nuclear deal that Tehran had continued to honour.

"Today we are in a faceoff with America in which there is no one in the world that does not praise Iran," Rouhani said in a speech broadcast live on state television.

"Iran has been loyal to its signature, Iran has been loyal to international agreements, and the one standing against us today is the one that has trampled all pacts, agreements and international accords," he added.

Iran is locked in a tense standoff with the US after Washington withdrew last year from the 2015 nuclear deal and reimposed sweeping sanctions, even as its allies said Tehran had abided by the agreement's terms.

Tensions have escalated ever since, with Washington bolstering its military presence in the region, blacklisting Iran's elite Revolutionary Guards as a terrorist organisation and blaming Tehran for twin attacks on tankers last week in the Gulf of Oman.

Rouhani announced on May 8 that Iran would stop observing some restrictions on its stocks of enriched uranium and heavy water agreed under the deal, a move he said was in retaliation for the unilateral US withdrawal.

Tehran has threatened to go even further in scaling down nuclear commitments unless remaining partners to the deal — Britain, China, France, Germany and Russia — help it circumvent US sanctions.