New York City ? In a setback for the United States, Iran won a two-month reprieve from new U.N. sanctions over its nuclear program on Friday. The Bush administration and its European allies ceded to Russian and Chinese demands to give Tehran more time to address international concerns.

An agreement reached in talks here between six key nations and supported by the European Union gives Iran until November to make progress in answering questions about the program that the United States and others alleged is a cover for nuclear weapons development.

The decision marks another blow for Washington in its diplomatic struggle to toughen existing U.N. sanctions on Iran, whose leader this week declared to the U.N. General Assembly that the nuclear issue was “closed” and vowed to defy attempts to add new penalties.

The Bush administration had hoped to capitalize on growing international frustration with President Mahmoud Ahmadinejad’s hardline stance in refusing to halt uranium enrichment and reprocessing that he insists are purely for peaceful civilian energy use.