Mann said work on amending the EU regulations was already beginning, but cautioned that changes depend on the Iranian government living up to its end of the deal.
"It's important that both sides of the bargain are implementing this agreement, so we would coordinate timing-wise also with the Iranian side," the EU spokesman said.
Britain's Foreign Secretary William Hague put the total estimated value of sanctions relief at $7 billion over a 6-month period, but stressed it would not all come at once.
"They do not receive 7 billion on the first day and then decide if they want to implement their side of the agreement," Hague said, calling the amount of sanctions relief "a very small proportion" of the total frozen assets and value of sanctions applied to Iran.
"The way we're doing sanctions relief leaves Iran with a huge incentive" to go for a comprehensive agreement since Tehran wants complete sanctions relief, Hague said.
The deal reached Sunday will allow Iran to keep the central elements of its uranium program, while stopping its enrichment at a level lower than what is needed for nuclear arms. In addition to a six-month window for Iran to allow more U.N. access to nuclear sites, sanctions will be eased notably in the oil, automotive and aviation industries though not ended.
The agreement is a first step one that Israel has condemned as a "historic mistake" that effectively accepts Iran as a threshold nuclear weapons state. Israel has found common cause with Saudi Arabia, which shares concerns about a nuclear-armed Iran and Tehran's growing regional influence.
On his return to Tehran, Iranian Foreign Minister Mohammed Javad Zarif told state television that the country was prepared for quick follow-up negotiations to keep the deal on track.
"We are ready to begin the final stage of nuclear agreement from tomorrow," said Zarif, who was greeted by hundreds of cheering students.
Many Iranians appeared upbeat about the deal and the possibility of an eventual end to sanctions, such as blocks on access to international banking networks that have crippled businesses and made once-routine transactions such as paying tuition for a student abroad a complicated process.
In the U.S., President Barack Obama defended the agreement, declaring that the United States "cannot close the door on diplomacy."
"Tough talk and bluster may be the easy thing to do politically, but it's not the right thing to do for our security," he said during an event in San Francisco.
But hardline groups in Iran remained highly wary of any close cooperation with Washington.
An editorial in the conservative daily Kayhan described the U.S. as a deceitful power that could renege on its pledges even if Iran sticks with its part of the deal.
"The U.S. was not trustworthy. The Geneva deal lasted only one hour," it said in its front-page headline, referring to U.S. Secretary of State John Kerry's comments that there was no recognition of Iran's "right" to enrich uranium.
Iran insists that trying to block enrichment was a dead end. For Iran's leaders, self-sufficiency over the full scope of its nuclear efforts from uranium mines to the centrifuges used in enrichment is a source of national pride and a pillar of its self-proclaimed status as a technological beacon for the Islamic world.
In the end, Iran agreed to cap its enrichment level at 5 percent, far below the 90 percent threshold needed for a warhead. Iran also pledged to "neutralize" its stockpile of 20 percent enriched uranium the highest level acknowledged by Tehran by either diluting its strength or converting it to fuel for research reactors, which produced isotopes for medical treatments and other civilian uses.
In return, Iran got the rollback in some sanctions a total package the White House also estimated will re-inject $7 billion into the Iranian economy but the main pressures remain on Iran's oil exports and its blacklist from international banking networks during the first steps of the pact.
Despite Obama's assurances that no new sanctions will be levied on Iran while the interim agreement is in effect, some U.S. lawmakers want to push ahead with additional penalties. A new sanctions bill has already passed the House of Representatives, and if it passes the Senate, Obama could have to wield his veto power in order to keep his promise to Tehran.
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Murphy reported from Dubai, United Arab Emirates. Associated Press writers Matthew Lee in Washington, Lori Hinnant in Paris and Ali Akbar Dareini in Tehran contributed to this report.
