President Hassan Rouhani has hailed a nuclear deal with world powers as a "golden page" in Iran's history, hours after lifting of economic sanctions.
But in an address to Parliament he noted bitter opposition to Saturday's (local time) lifting of economic curbs from arch foe Israel, some members of the US Congress and what he called "warmongers" in the region - an apparent reference to some of Iran's Gulf Arab adversaries.
Iran ended years of economic isolation when world powers lifted the crippling sanctions against the Islamic Republic on Saturday in return for Tehran complying with a deal to curb its nuclear ambitions.
Presenting the draft budget for the next Iranian fiscal year, which begins in March, Rouhani told parliament the deal was a "turning point" for the economy of Iran, a major oil producer that has been virtually shut out of international markets for the past five years.
"The nuclear negotiations which succeeded by the guidance of the Supreme Leader and support of our nation, were truly a golden page in Iran's history," Rouhani said.
"The nuclear deal is an opportunity that we should use to develop the country, improve the welfare of the nation, and create stability and security in the region."
In a dramatic move that coincided with the scrapping of the sanctions, Tehran also announced the release of five Americans, including Washington Post reporter Jason Rezaian, as part of a prisoner swap with the United States.
Together, the lifting of sanctions and the prisoner deal help to ease the hostility between Tehran and Washington that has shaped the Middle East since Iran's 1979 Islamic Revolution.
Tens of billions of dollars' worth of Iranian assets will now be unfrozen and global companies that have been barred from doing business there will be able to exploit a market hungry for everything from cars to aeroplane parts.
However, America's thaw with Iran is viewed with deep suspicion by US Republicans as well as allies of Washington in the Middle East, including Israel and Saudi Arabia.
Israel's opposition was evident in a statement from the office of Prime Minister Benjamin Netanyahu on Saturday night.
"Even after the signing of the nuclear agreement, Iran has not abandoned its aspirations to acquire nuclear weapons, and continues to act to destabilise the Middle East and spread terrorism throughout the world while violating its international commitments," the statement said.
Rouhani took a swipe at its critics. "Everybody is happy except the Zionists, the warmongers who are fuelling sectarian war among the Islamic nation, and the hardliners in the US congress," he said.
The International Atomic Energy Agency ruled on Saturday that Iran had abided by an agreement last year with six world powers to curtail its nuclear program, triggering the end of sanctions.
Minutes after the IAEA's ruling, the United States formally lifted banking, steel, shipping and other sanctions on Iran. The European Union likewise ended all nuclear-related economic and financial sanctions against the country.
The IAEA's confirmation that Iran had fulfilllled its commitments under the nuclear deal also automatically ended most United Nations sanctions on the country.
The end of sanctions means more money and prestige for Shi'ite Muslim Iran as it becomes deeply embroiled in the sectarian conflicts of the Middle East, notably in the Syrian civil war where its allies are facing Sunni Muslim rebels.
Iran denies its nuclear program was aimed at obtaining an atomic bomb. Washington maintains separate, less comprehensive sanctions on Iran over its missile program.
In Washington, US President Barack Obama pardoned three Iranian-Americans charged with violating sanctions against Iran, a lawyer for one of the men said, while prosecutors moved to drop charges against four Iranians outside the United States.