By ALI AKBAR DAREINI and JOHN-THOR DAHLBURGTEHRAN, Iran (AP) a¿¿ Iran unplugged banks of centrifuges involved in its most sensitive uranium enrichment work on Monday, prompting the United States and European Union to partially lift economic sanctions as a landmark deal aimed at easing concerns over Iran's nuclear program went into effect. The mutual actions a¿¿ curbing atomic work in exchange for some sanctions relief a¿¿ start a six-month clock for Tehran and the world powers to negotiate a final accord that the Obama administration and its European allies say will be intended to ensure Iran cannot build a nuclear weapon. In the meantime, the interim deal puts limits on Iran's program a¿¿ though it continues low levels of uranium enrichment. Tehran denies its nuclear program is intended to produce a bomb. The payoff to Iran is an injection of billions of dollars into its crippled economy over the next six months from the suspension of some sanctions a¿¿ though other sanctions remain in place. In part a reflection of a thaw between Washington and Tehran, the moves coincidentally occurred on the 33rd anniversary of the end of the Iran hostage crisis. The holding of 52 Americans for 444 days by radical Iranian students that ended Jan. 20, 1981 was followed by more than three decades of U.S.-Iranian enmity that only began to ease last year with signs that Iran was ready to meet U.S. demands and scale back its nuclear activities. British Foreign Secretary William Hague called the deal "an important milestone" a¿¿ but not the ultimate goal. "It's important that other sanctions are maintained and the pressure is maintained for a comprehensive and final settlement on the Iranian nuclear issue," Hague said. The Europeans are aiming to start negotiations on a final deal in February, though no date or venue has been agreed on yet. Iranian Foreign Minister Mohammad Javad Zarif said Saturday that Tehran is ready to enter talks as soon as the interim deal goes into force.