A prominent hardline cleric in Iran warned on Friday against the Islamic republic resuming ties with the United States, and said any attempt to do so would prove futile.
"Some people have created an underground network for establishing relations with the America," Ayatollah Ahmad Janati told crowds at Friday prayers in Tehran, in comments broadcast by state media.
"Our people are anti-American -- you should be anti-American as well. Why did you go a different way from the people?" Janati asked, addressing those alleged to be behind the move.
"As long as our people and our supreme leader do not want it, your efforts will not bear any fruit," added Janati, who heads the powerful Guardians Council electoral watchdog.
His comments sparked chants of "Death to the America!" and "Death to Israel!" from the thousands of Friday worshippers.
Supreme leader Ayatollah Ali Khamenei has the final say on all Iranian state matters including foreign policy and the nuclear issue.
Icy ties between Tehran and world powers have thawed since President Hassan Rouhani, a moderate, defeated a pool of conservatives in last June's presidential election after vowing to engage constructively with the West.
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The most remarkable development to date was a 15-minute telephone conversation between Rouhani and his US counterpart Barack Obama in New York in September.
It was the first direct contact between the leaders of the two nations since diplomatic ties were severed after the US embassy hostage crisis in Tehran from 1979-1981.
But Khamenei later said he deemed part of Rouhani's New York trip as inappropriate, but without referring directly to the phone call.
The two countries' foreign ministers, Mohammad Javad Zarif and John Kerry, have also met several times, most recently at the Munich International Security Conference.
Zarif has gone so far as to tell Russian television that Washington could one day reopen its embassy in Tehran.
Iran's hardliners and many lawmakers are also critical of a landmark nuclear agreement agreed in November.
They question what Tehran stands to gain from the deal, under which it agreed to roll back parts of its controversial nuclear drive for six months in exchange for modest sanctions relief.
Western nations and the country's arch-enemy Israel have long suspected Iran of covertly seeking nuclear weapons alongside its civilian programme, an allegation denied by Tehran.
The conservative-dominated parliament has frequently summoned Zarif and other ministers for questioning on a variety of issues, including the Zarif-Kerry meetings.