Vienna, Austria ? Just a day before an international deadline, Iran agreed Sunday not to test any centrifuges as part of a total suspension of nuclear activities that can yield uranium for atomic weapons. Diplomats described the about-face as an effort to avoid possible U.N. sanctions.

Diplomats from the European Union and elsewhere said on condition of anonymity that the International Atomic Energy Agency received a letter from Iran containing a pledge not to test 20 centrifuges during the freeze it agreed to Nov. 7 during negotiations with Britain, France and Germany, who were working on behalf of the European Union.

The pledge appeared to resolve a dispute that threatened to escalate at today’s IAEA board meeting into consultations on possibly referring Iran to the U.N. Security Council for defying the board. The Security Council could then impose sanctions against Iran.

A senior diplomat with nuclear expertise told The Associated Press the Iranian pledge appeared to contain no pitfalls and seemed to meet the European demands.

Still, the commitment came with strings attached. A government official from a board member country told The AP that France, Germany and Britain had accepted an Iranian demand to further water down the language of a draft resolution they wrote for adoption by the board on ways of policing the suspension.

The text to be adopted today now includes a phrase emphasizing that the suspension is not a legal or binding obligation on Tehran’s part, he said.