WASHINGTON?President Bush’s top advisers say the United States must be prepared to use nuclear weapons to deter attacks involving weapons of mass destruction. But in an effort to ease alarm overseas, they said there were no plans to do so.

“We all want to make the use of weapons of mass destruction less likely,” national security adviser Condoleezza Rice said Sunday.

Rice, Secretary of State Colin Powell and military and congressional leaders were responding to weekend reports that the Pentagon has told Congress it is studying the possible use of nuclear weapons against countries that threaten the United States.

The classified “nuclear posture review” sent to Congress says the Pentagon is developing contingency plans for using nuclear weapons against countries that are developing weapons of mass destruction, including China, Iran, Iraq, Libya, North Korea, Russia and Syria.