U.S. Homeland Security Secretary Tom Ridge announced Tuesday that he is leaving his post as part of what is turning into a major cabinet reshuffle for President George Bush's second term.

It had been widely expected that Secretary Ridge would leave the administration and return to private life once the president won re-election, and he made it official during a Washington news conference.

"The president has given me an extraordinary opportunity to serve my country in this incredible period since September 11th, 2001," he said. "I will always be grateful for his call to service."

Mr. Ridge says he is not sure what he will do next. But he says that after 22 years of government service, he is looking to make personal and family matters a higher priority.

Tom Ridge became the first White House Homeland Security adviser shortly after the September 11th, 2001, terrorist attacks on New York, Washington and Pennsylvania. He went on to become the first secretary of Homeland Security in January of last year after Congress passed legislation setting up the department by merging 180,000 employees from 22 government agencies.

Mr. Ridge says he believes the country is more secure than it was before the 2001 attacks but that more needs to be done.

"I am also confident that based on what detainees have told us that if you increase your security and your vigilance that is a deterrent," he said. "Can I tell you today that there are 'x' number of incidents that we were able to thwart or prevent? I cannot. Am I fairly confident that we probably have? Yes, I am, but it is still difficult to prove something unless I can point to a specific case."

Mr. Ridge will be remembered for establishing the color-coded security alert system that Americans have now accepted as part of the war on terror. But that color chart also became occasional fodder for late night comedians on U.S. television.

Tom Ridge is a former congressman and governor from Pennsylvania who is also a decorated veteran of the Vietnam War. He is the latest of several Bush cabinet members to announce their intention to leave the administration as the president prepares to begin his second term on January 20.

Secretary Ridge says he will stay on until February 1 to give the administration time to name a successor, who must be confirmed by the Senate. Administration officials have not indicated as yet who will succeed him.