President Bush marked the third anniversary of the Sept. 11, 2001, hijackings by plugging his Iraq policy in a live broadcast yesterday from the Oval Office, and Sen. John F. Kerry followed a tearful memorial service by criticizing the president for hiding a report on intelligence gathering.

In the latest expression of the presidential campaign's pace and tone, the candidates paused to solemnly mark the attacks that killed nearly 3,000 and transformed Bush's presidency -- then quickly returned to differences over his worthiness to continue as commander in chief in the war on terrorism.

Bush typically tapes his Saturday radio address in advance, but yesterday he read it live from his desk in the company of New York firefighters and police officers; parents, children, grandchildren and spouses of pilots and passengers who were lost that day; and rescue workers who served the Pentagon.

The president began by recalling the morning three years ago when "the struggle of good against evil was compressed into a single morning," and he remembered "the images of fire, and the final calls of love, and the courage of rescuers who saw death and did not flee." He went on to say that he is "determined to stay on the offensive" in battling terrorists.

"Our present work in Iraq and Afghanistan is difficult," Bush said. "It is also historic and essential. By our commitment and sacrifice today, we will help transform the Middle East and increase the safety of our children and grandchildren."

Former solicitor general Theodore B. Olson and his three granddaughters were among the guests; his wife, conservative commentator Barbara Olson, was aboard American Airlines Flight 77, which crashed into the Pentagon. After the address, the White House posted on its Web site a six-page "fact sheet" titled "Three Years of Progress in the War on Terror," with such assertions as, "The Bush Administration has made an unprecedented commitment to homeland security."

In the moments before 8:46 a.m. -- the time when the first hijacked plane hit the World Trade Center three years earlier -- a hushed crowd of a few hundred survivors, rescuers and Bush aides gathered on the South Lawn of the White House. The Marine band played "God of Our Fathers," followed by "America the Beautiful" from the porch beneath the Truman Balcony. On the roof, the flag flew at half-staff. Butlers and other grounds and household staff members lined two spiral staircases leading to the lawn.

Then the doors of the Diplomatic Reception Room opened, and the president and first lady Laura Bush, accompanied by Vice President Cheney and his wife, Lynne, walked out onto the lawn and bowed their heads in a moment of silence as a Marine bugler played taps. The president and first lady patted each other on the back as they strolled back inside.

Bush began the day with a prayer service at St. John's Episcopal Church, across Lafayette Square from the White House. Frances Townsend, his homeland security adviser, read from Philippians 4, which offers assurance of "the peace of God, which surpasses all understanding."

In Massachusetts at about the same time, Kerry attended a flower-laying ceremony at the Boston Public Garden's Garden of Remembrance, a horseshoe-shaped memorial dedicated to Sept. 11 victims. A small plane towing a huge American flag flew overhead as Kerry lingered over the engraved inscription of the names of Massachusetts victims of the attacks.

Both planes that hit the Trade Center's two towers had taken off from Boston's Logan International Airport. At 8:46 a.m., the senator from Massachusetts placed lilies on the low granite memorial.

Later, at an anniversary commemoration at the Boston Opera House, Kerry spoke of the spirit "which will guide us all as we rebuild those towers -- stronger, higher and more beautiful than ever before. Just like America."

Current plans for redeveloping Ground Zero call for an anchor of a single tower. Aides said Kerry's reference was a metaphor for dreams and ideals.

At 12:15 p.m., Kerry's campaign e-mailed a statement calling on Bush to declassify and release a report on the nation's intelligence services by a presidential advisory panel headed by retired Lt. Gen. Brent Scowcroft.

"The White House has held this important report under wraps for nearly three years while resisting efforts to strengthen the intelligence services that are essential to preventing terrorist attacks and protecting our nation," Kerry said. "What is the White House hiding?"

Bush-Cheney campaign spokesman Reed Dickens replied: "We'll respond tomorrow to the Kerry attacks. Today is a day of remembrance."

Staff writer Paul Farhi in Boston contributed to this report.