In its drive to stop Iran gaining any ability to make nuclear weapons, the United States is ready to give European allies only until June to cajole Tehran before Washington seeks U.N. sanctions, U.S. diplomatic documents show.

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Rohani also said Washington could do more to help the negotiations. During Bush's visit, European leaders tried to persuade him to join their diplomatic initiative.

The United States has so far refused to participate in a plan it believes is doomed to failure. But Bush said he would at least think about actively joining forces with the Europeans.