Senior officials say President Bush plans to name National Security Advisor Condoleezza Rice to replace Colin Powell as secretary of state.
Ms. Rice is known to be one of President Bush's most trusted aides and a strong supporter of the Iraq war.
Sources say her deputy, Stephen Hadley, will replace her as national security advisor and that the president could make both announcements as early as Tuesday.
Mr. Powell, seen as a moderate within the Bush administration, resigned Monday. He told reporters he always intended to serve only one term. He said he and President Bush had reached "mutual agreement" that it was time for him to move on.
The secretaries of agriculture, energy and education also resigned Monday. Such cabinet re-shuffles are not unusual for second-term U.S. presidents.