Iran's supreme leader Ayatollah Ali Khamenei said any negotiations with the US would be like "going on your knees before the enemy and kissing the claws of the wolf."
Iran's supreme leader said on Wednesday that any negotiations with the US would "bring nothing but material and spiritual harm" in remarks before an American-led meeting on the Middle East in Warsaw.
The comments from Ayatollah Ali Khamenei were part of a seven-page statement read word-for-word on Iranian state TV and heavily promoted in the run-up to its release.
They also come two days after Iran marked the 40th anniversary of its 1979 Islamic Revolution amid heightened tensions between Tehran and Washington.
"About the United States, the resolution of any issues is not imaginable and negotiations with it will bring nothing but material and spiritual harm," Khamenei said.
The supreme leader went on to describe any negotiations as an "unforgiveable mistake." He also said negotiations would be like "going on your knees before the enemy and kissing the claws of the wolf."
In 2015 Khamenei approved of talks between Iran and the United States that resulted in the nuclear deal between Tehran and world powers. The deal saw Iran limit its enrichment of uranium in exchange for the lifting of economic sanctions.
However, that deal came under the administration of former president Barack Obama.
Khamenei said the US must deal with Iran's influence in the Middle East and "preventing the transference of sophisticated Iranian weapons to resistance forces."
'Not ready to accept bullying'
Iranian President Hassan Rouhani, during a Cabinet meeting Wednesday, echoed Khamenei's remarks, saying "If the Iranian nation surrenders to the United States, it should surrender until the end."
He said, however, that "Iran is about negotiation, but we are not ready to accept imposition, bullying, pressure and the trampling of our national rights."
President Donald Trump, who campaigned on a promise of tearing up the nuclear accord, withdrew the US from the deal last May. Since then, the United Nations says Iran has kept up its side of the bargain.
Amid the new tensions, Iran's already-weakened economy has been further challenged.
The Warsaw summit, which started on Wednesday, was initially pegged to focus entirely on Iran. However, the US subsequently made it about the broader Middle East, to boost participation.
Iranian Foreign Minister Mohammad Javad Zarif predicted the Warsaw summit would not be productive for the US.
"I believe it's dead on arrival or dead before arrival," he said.