WASHINGTON (AP) - The United States will begin easing economic sanctions on Iran after it began shutting down its most sensitive nuclear work on Monday, the White House said.

Iran's move was part of a landmark deal struck late last year with the U.S., five other world powers and the European Union to ease concerns over Tehran's nuclear program and provide for the partial removal of some of the economic sanctions that have crippled the Iranian economy. Iran has insisted that its nuclear program was for peaceful purposes only.

The United Nations nuclear agency, the International Atomic Energy Agency, confirmed Monday that higher-level uranium enrichment at a facility in central Iran had stopped, an important step among others that together provided officials with the evidence needed to conclude that Iran was holding up its end of the agreement.

The White House, which has vowed to prevent Iran from developing nuclear weapons, hailed Iran's actions as "an important step forward."

"These actions represent the first time in nearly a decade that Iran has verifiably enacted measures to halt progress on its nuclear program, and roll it back in key respects," White House press secretary Jay Carney said in a statement. "Iran has also begun to provide the IAEA with increased transparency into the Iranian nuclear program, through more frequent and intrusive inspections and the expanded provision of information to the IAEA. Taken together, these concrete actions represent an important step forward."

The European Union announced earlier Monday that it, too, was suspending some of the sanctions it has imposed on Iran.

Carney said the five world powers - the United Kingdom, France, Germany, Russia and China - also would begin providing relief to Iran.

At the same time, Carney said the group will continue its aggressive enforcement of sanctions that will remain in effect during the next six months, the period that Iran and the world powers will use to negotiate a final deal.