In an speech at a Tehran mosque punctuated by chants of "Death to America" and "Death to Israel", Khamenei said he wanted politicians to examine the agreement to ensure national interests were preserved, as Iran would not allow the disruption of its revolutionary principles or defensive abilities.
An arch conservative with the last word on high matters of state, Khamenei repeatedly used the phrase "whether this text is approved or not", implying the accord has yet to win definitive backing from Iran's factionalized political establishment.
"Whether the deal is approved or disapproved, we will never stop supporting our friends in the region and the people of Palestine, Yemen, Syria, Iraq, Bahrain and Lebanon. Even after this deal our policy towards the arrogant US will not change," he said.
Under the agreement reached on Tuesday, sanctions will be gradually removed in return for Iran accepting long-term curbs on a nuclear program that the West has suspected was aimed at creating a nuclear bomb. Iran denies it seeks a nuclear bomb.
Khamenei's combative remarks about US policies in the Middle East may sit awkwardly with a diplomatic offensive Foreign Minister Mohammad Javad Zarif plans in coming days in the wake of the deal.
'Insult'Iran regards its nuclear program as an emblem of national dignity and dynamism in the face of what it sees as decades of hostility from Western countries that opposed its 1979 Islamic revolution.
Khamenei did not echo criticisms of the deal made on Friday by a top cleric, Ayatollah Mohammad Ali Movahedi Kermani, who said in an address broadcast on radio that it reflected excessive demands by world powers that were an "insult".
But Khamenei's remarks radiated a broad mistrust of US intentions, claiming that successive American presidents had sought Iran's "surrender", and declaring that if war broke out America would come off worst, nursing "a broken head".
"The Americans say they stopped Iran from acquiring a nuclear weapon," Khamenei said.
"They know it's not true. We had a fatwa (religious ruling), declaring nuclear weapons to be religiously forbidden under Islamic law. It had nothing to do with the nuclear talks."
Later on Saturday, the Supreme Leader praised Iranian negotiators who thrashed out the accord in marathon negotiations in Vienna.
"During the nuclear talks, we saw the Americans' dishonesty over and over, but fortunately our officials fought back and in some cases showed revolutionary reactions," Khamenei said during meetings with senior Iranian officials and ambassadors from several Muslim states, according to his official website.
But his remarks on Saturday did not shed light on Iran's procedures for ratifying the accord, which are not known in any detail. Zarif will brief parliament on July 21, Iranian media have said, and the agreement will also be examined by the National Security Council, the country's highest security body.
Zarif, who plans to visit several countries in the region, told fellow Muslim countries on Friday that Iran hoped the accord could pave the way for more cooperation in the Middle East and internationally.
In a message to Islamic and Arab countries on the Eid al-Fitr holiday at the end of Ramadan, Zarif said: "By solving the artificial crisis about its nuclear program diplomatically, a new opportunity for regional and international cooperation has emerged."
Khamenei maintained that the Islamic Republic's policies in the region would continue to defy the United States, and the nuclear deal was an exceptional instance of dialogue.
"We have repeatedly said we don't negotiate with the US on regional or international affairs; not even on bilateral issues. There are some exceptions like the nuclear program that we negotiated with the Americans to serve our interests."
He said US policies in the region were "180 degrees" opposed to Iran's policies.
"The Americans dub the Lebanese resistance terrorists and regard Iran as a supporter of terrorism because of its support for the Lebanese Hezbollah, while the Americans themselves are the real terrorists who have created Islamic State and support the wicked Zionists," Khamenei said.
Several Gulf Arab states have long accused Tehran of interference, alleging financial or armed support for political movements in several countries including Bahrain, Yemen and Lebanon. Shi'ite power Iran denies interference but vows undimmed support for the Syrian and Iraqi governments, who are both fighting insurgencies by a variety of Sunni armed groups.
Prominent conservatives have largely kept silent on the deal. Ali Akbar Velayati, a senior advisor to Khamenei, did not mention the agreement in his Eid al-Fitr message.
"If any of our security officials or members of parliament approve or denounce the deal before fully scrutinizing it, they will regret it," Revolutionary Guard commander and head of Iran's Basij organization, Mohammad Reza Naghdi told the Fars news agency on Friday.