U.S. Defense Secretary Donald Rumsfeld said Monday he has no plans to quit his post, as opposition Democrats and some retired generals renewed calls for his replacement. I m not, Rumsfeld replied when asked by a reporter if he was considering resigning. Critics of the defense chief have called for Rumsfeld s resignation over his management of the U.S. military operation in Iraq, which has cost $300 billion and the lives of more than 2,600 U.S. soldiers. In April, Rumsfeld confronted a revolt by retired generals who accused him of being responsible for errors committed in the war in Iraq and called for his removal. But President George W. Bush stood by his defense chief. Two years ago, during the Abu Ghraib prison scandal, Rumsfeld reportedly offered to resign, but Bush refused to accept it.