A deal with world powers ended a "manufactured crisis" over Iran's nuclear program, its foreign minister says, as he arrived home from negotiating the agreement that has angered US lawmakers.  As attention turned to the lengthy process of implementing the complex accord, Mohammad Javad Zarif said on Wednesday the world had no cause to fear Iran's nuclear activities.  Zarif, who led Iran's negotiating team in the 18 straight days of "tough" talks that culminated in Tuesday's historic agreement, said common ground had been found.  "We will take measures and they will do their part," he told reporters at Tehran's Mehrabad airport, referring to the six powers led by the United States with whom Iran is now bonded in the nuclear pact.  "It will happen in around four months from now," he said of the formal implementation of the deal.  Zarif's comments came after a night of celebrations in Tehran where his own name was chanted in the streets by joyous Iranians.  Many festooned their cars with balloons and danced on the street to celebrate the prospect of an end to the long years of economic hardship caused by Western sanctions.  But only hours earlier in Washington, the deal came under intense scrutiny.  The speaker of the Republican-led US House of Representatives, John Boehner, said the agreement was "likely to fuel a nuclear arms race around the world".  Zarif hit back at the deal's biggest critic, Israeli Prime Minister Benjamin Netanyahu, head of the region's sole if undeclared nuclear state, who branded the agreement a "historic mistake".  "Netanyahu kicked up a fuss as he is upset that Iran managed to get sanctions lifted and prevent a manufactured crisis," Zarif said.  Iran has always denied seeking an atomic bomb and that stance was reiterated by President Hassan Rouhani after Tuesday's agreement.  Soon after the deal was announced, the White House launched a campaign to stop sceptics at home and abroad from derailing the hard-won accord.  US President Barack Obama was to hold a press conference later on Wednesday to try to convince Americans of the benefits of the deal, which is likely to face a bruising passage through congress.  US lawmakers have 60 days to review the accord, but Obama has vowed to use his presidential veto over any attempt to block it.  Obama said the accord meant "every pathway to a nuclear weapon is cut off".  "This deal offers an opportunity to move in a new direction. We should seize it," he said, pointing to a broader effort to end the hostility between the two governments that has persisted ever since the overthrow of the US-backed shah in the Islamic revolution of 1979.  Washington hopes the accord may lead to more co-operation with Iran at an explosive time in the Middle East after the Islamic State militant group surged last year, seizing vast swathes of Syria and Iraq.  Russian Foreign Minister Sergei Lavrov said the deal paves the way for a "broad" coalition to fight the Sunni extremist group which is as hostile to Shi'ite Iran as it is to the West.  "It removes the barriers - largely artificial - on the way to a broad coalition to fight the Islamic State and other terrorist groups," Lavrov said.  EU foreign policy chief Federica Mogherini told Sky Italia the deal "opens the way for a new confidence" in combating IS.  But it has alarmed some of America's most important Middle East allies, including Sunni regional power Saudi Arabia.  Do you have any news photos or videos?
Iran and the six major powers have struck a deal that would curb Tehran's nuclear program in return for the lifting Western sanctions.