WASHINGTON, July 15 (Xinhua) -- U.S. Secretary of State Hillary Clinton said on Wednesday that Iran's recent crackdown on post-election protesters was "deplorable and unacceptable", warning that the U.S. patience to engage Iran is limited.

    In extracts of a speech she plans to deliver to the Council on Foreign Relations, Clinton said that "We remain ready to engage with Iran, but the time for action is now."

    Clinton said that the United States understands "the importance of trying to engage Iran and offering its leaders a clear choice: whether to join the international community as a responsible member or to continue down a path to further isolation.

    However, the top U.S. diplomat noted that "Neither the president nor I have any illusions that direct dialogue with the Islamic Republic will guarantee success."

    "The opportunity will not remain open indefinitely," she said.