Iranian Supreme Leader Ayatollah Ali Khamenei said Iran's interaction with the United States should be limited to "very rare and specific" cases such as nuclear talks.
Speaking to the Iranian ambassadors and Foreign Ministry officials on August 13, Khamenei said Iran should interact with all countries, except the United States and Israel.
Khamenei, who has the final say in all state matters, has backed negotiations with world powers, including the United States, over Iran's contested nuclear programs.
However, he criticized the United States, saying direct talks with its diplomats didn't reduce sanctions or decreased its animosity toward Iran.
Khamenei pointed out that he "will not ban" the nuclear talks, saying he supported Foreign Minister Javad Zarif and his nuclear negotiation team.
But the Supreme Leader said engaging in negotiations with the United States "has become yet another invaluable experience that interaction and talks with Americans have absolutely no effect in easing their animosity."
A recent interim nuclear deal saw Iran curb portions of its nuclear program in exchange for an easing of some sanctions.
Iran and world powers have not yet reached a final nuclear deal.
Khamenei said holding more negotiations with the United States would only prepare the ground for Washington to make more demands.
And he said sitting at a negotiating table with the Americans offered a dubious image of Iran to the world.
In June, U.S., Iraq, and Iranian officials reportedly met on the sidelines of nuclear negotiations in Vienna, to discuss the raging Sunni Islamist insurgency in Iraq.
During the meeting Khamenei also reiterated Iran's support to Iraq's new prime minister-designate, Haidar al-Abadi.
This week, both Washington and Tehran swiftly backed Baghdad's decision to nominate Abadi to replace Nuri al-Maliki as prime minister.
Maliki, a Shi'ite, had enjoyed the support of Shi'ite Iran, but officials said recently that Tehran believed Maliki was no longer able to hold the country together.
Khamenei said: "I hope the designation of the new prime minister in Iraq will untie the knot and lead to the establishment of a new government and teach a good lesson to those who aim for sedition in Iraq."
Maliki, Iraq's premier since 2006, has been accused of fueling sectarian violence as Iraq is battling an Islamist insurgency, but he has rejected calls to step down.