In his first public comments on a European-brokered agreement for Iran to boost cooperation with the International Atomic Energy Agency (IAEA), the all-powerful leader stressed the country had scored a diplomatic victory against what he described as a "Zionist-US conspiracy".
"There was no surrender in it," Khamenei was quoted as telling a gathering of top officials in a report overnight Sunday by the official IRNA news agency.
"What happened was right and well managed in order to foil the US and Zionist conspiracy."
The IAEA had given Iran until the end of October to fully disclose details of its nuclear programme, and urged it to allow a tougher inspections regime by signing an additional protocol to the Non-Proliferation Treaty (NPT). Iran was also called upon to suspend uranium enrichment.
After initially rejecting the deadline, Iran agreed to comply just 10 days before it expired, during an unprecedented joint visit here by the foreign ministers of Britain, France and Germany, Jack Straw, Dominique de Villepin and Joschka Fischer.
But Khamenei warned the Europeans that they also had to live up to their commitments -- providing technical assistance if the IAEA deems that Iran has cooperated, and a pledge that tougher inspections will not infringe on Iranian sovereignty.
"If the discussions with the Europeans continue in the way they have been going, we will continue. But if parties in the dialogue or our enemies want to step in and show excessiveness, everything will be disrupted," he said.
"If we reach the point where our national interests and the regime's values are tarnished, we will have no doubts about cutting off this process."
Khamenei, who was speaking during an iftar meal -- the evening dinner that breaks the daytime fast observed by Muslims during the holy month of Ramadan -- also warned that "the regime's enemies should not imagine that the Islamic republic is trapped."
The term "enemies" usually applies to the United States and Israel, both of which allege Iran is using its atomic energy programme as a cover for nuclear weapons development.
But amid opposition to the nuclear accord from some hardliners -- many of whom have called for Iran to follow the path of North Korea and pull out of the NPT altogether -- Khamenei appealed for unity behind the deal.
"This issue should not bring about differences. Officials, intellectuals, the press, MPs, Friday prayer leaders and those who have access to public podiums have a very heavy resposibility," he said.
And Khamenei reiterated Iran's determination to generate nuclear power, touted by officials here as crucial for meeting future energy needs.
Part of this, he said, was Iran's mastering of the complete nuclear fuel cycle. This is something the European foreign ministers would rather see kept out of the country -- hence calls for a suspension of uranium enrichment here and an unwritten pledge of eventual nuclear fuel supplies.
"Some countries say that Iran does not need to produce nuclear fuel. These countries are trying to take charge of providing Iran with nuclear fuel for its plants in order to take Iran and Iranians hostage and put pressure on the Islamic republic," Khamenei said.
"But, based on international regulations, we will produce nuclear fuel," he said, warning that: "If anyone wants to challenge the Islamic republic in the area of peaceful nuclear activity or interfere in our internal affairs, they will get a blow to the mouth."
Reformist President Mohammad Khatami, who was also present at the meeting, emphasised that "Iranian officials did not commit themselves to something that is irreversible.
"It is the other side that has to keep its word and promises," he said.