President Bush is downplaying criticism of his Iraq policy from a former member of his Cabinet. Mr. Bush says his decision to take military action was difficult, but the right thing to do.

The president is watching his words when it comes to responding to Paul O'Neill.

Mr. O'Neill served as treasury secretary until December 2002. In a new book, he says that President Bush was intent on invading Iraq when he assumed office, and was looking for a way to do it even before the September 11, 2001, terrorist attacks on the United States. He repeated that assertion in an interview broadcast Sunday on the CBS television network. "From the very beginning, there was a conviction that Saddam Hussein was a bad person and that he needed to go," he said.

The president's first public comments on the interview came during a joint news conference in Monterrey, Mexico, with Mexican President Vicente Fox. "I appreciate former Secretary O'Neill's service to our country. We worked together during some difficult times," he said.

He noted they worked together when America was in an economic recession, and again when the United States was attacked by terrorists. Mr. Bush said that attack made him realize that America was no longer protected by oceans, and threats had to be taken seriously. "And as the president of the United States, my most solemn obligation is to protect the security of the American people," he said.

Mr. Bush said he tried to work through the United Nations to disarm Saddam Hussein, and that he ultimately made the tough decision to use force when the former Iraqi leader ignored the world's demands.

Meanwhile, some treasury department officials say they want an investigation into the possibility Paul O'Neill improperly disclosed secret documents. They say they became concerned when a document marked "secret" was shown during Mr. O'Neill interview with CBS.