The governing board of the U.N. nuclear watchdog unanimously called on Iran on Thursday to halt sensitive atomic work it resumed this week in defiance of the West, a demand that Tehran rejected as unacceptable and illegal.

The resolution adopted by the board of governors of the International Atomic Energy Agency (IAEA) says Iran must resume full suspension of all nuclear-fuel-related activities and asks the agency to verify Tehran's compliance. Iran, which has denied Western accusations that its atomic program is a front for covert bombmaking, resumed work at its uranium conversion plant in Isfahan on Monday.

"The resolution on Iran was just adopted without a vote by consensus, full consensus. All 35 members of the board agreed" to the language of the resolution text, IAEA spokeswoman Melissa Fleming told reporters.

President Bush told reporters at his ranch near Crawford, Tex., that the decision of the U.N. nuclear watchdog to express concern about Iran's decisions was "a positive first step."

He said the U.S. strategy was is to work with Britain, France and Germany "so that the Iranians hear a common voice speaking to them about their nuclear weapons ambitions."

The IAEA board began meeting on Tuesday but adjourned to allow the European Union time to negotiate the resolution with board members. It reconvened on Thursday to approve the draft after days of backroom haggling over the text. The resolution, drafted by the three European countries, requests IAEA chief Mohamed ElBaradei "to provide a comprehensive report" by Sept. 3 on the status of Iran's program.

The text did not say that Iran should be referred to the U.N. Security Council, which has the power to impose sanctions.

In spite of calls from the E.U. and the United States not to resume work at the Isfahan plant, Tehran on Wednesday broke U.N. seals there and made the facility fully operational.

Iran says it needs to develop nuclear power as an alternative energy source to meet booming electricity demand and keep its oil and natural gas reserves for export.

E.U. diplomats said that if Iran does not comply, they will ask the board to refer the matter to the Security Council in September.

Iran rejected the resolution as unacceptable.

"We do not accept this resolution and will not execute it. There are serious legal problems with this resolution and . . . we are not obligated to implement it," Mohammad Saeedi, deputy head of Iran's Atomic Energy Organization, told state television. "There is no doubt that the uranium-conversion facility in Isfahan will continue operating, and we will continue relations with the agency and we will welcome inspections."

Sirus Naseri, right, representing Iran at IAEA meetings, said the country will continue efforts to produce nuclear fuel.