WASHINGTON — The United States will begin easing economic sanctions on Iran after it began shutting down its most sensitive nuclear work today, the White House said.

Iran’s move was part of a landmark deal struck 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 is for peaceful purposes only.

The United Nations nuclear agency, the International Atomic Energy Agency, confirmed today 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.”

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

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