Each year, the names of the nation's police officers killed in the line of duty are inscribed on the gray marble of the National Law Enforcement Officers Memorial in Washington. The list for 2001 is the longest ever.

Because of the Sept. 11 attack on the World Trade Center, 233 officers were killed last year, including 72 who responded to the attack. President Bush called it the saddest day in the history of law enforcement.

"We call all those we honor today — those who lost their life on 9/11 and those who lost their lives before and after 9/11 — heroes, because they are heroes," Bush told thousands of officers attending a U.S. Capitol ceremony. "Their families are proud of them, and always will be, yet there's not a husband or wife here today or a parent or a child who would not trade the honor to have them back."

Bush said Sept. 11 was a day of great horror and great heroism. He took with him to the ceremony the shield of Port Authority police officer George Howard, given to him by Howard's mother. Howard was one of 37 port authority officers who died Sept. 11. Bush said each of the nation's 700,000 sworn officers accept great responsibilities and great risk every day.

"Even in the most routine moments on watch or patrol, you protect us. Even on the quietest day, the next call may send you into extremes of danger. America is grateful. You just need to know, America is grateful."

After he spoke, Bush stood for a few moments before a memorial wreath.

Fox News' Wendell Goler and the Associated Press contributed to this report.