By Michelle Nichols, Arshad Mohammed and John Irish UNITED NATIONS (Reuters) - Three European powers have written to the U.N. Security Council detailing Iran's violations of its 2015 nuclear deal, a step diplomats said on Thursday aimed to pressure Tehran to resolve the issue diplomatically and to avoid reimposing U.

Diplomats say the U.N. nuclear watchdog’s board has censured Iran for failing to cooperate fully with the agency.

The International Atomic Energy Agency acted in the face of Iran’s refusal to allow experts to examine its stepped-up nuclear enrichment program.