President Bush (search) marked the Sept. 11 terrorist attacks Saturday by warning of continued danger to the United States and pledging victory over international terror.

"We will not relent until the terrorists who plot murder against our people are found and dealt with," Bush said in a rare live radio address from the Oval Office (search) to mark the third anniversary of the event that brought terrorism home to Americans.

Relatives of victims of the Sept. 11, 2001 (search), attacks, firefighters and other emergency responders surrounded the president as he spoke.

Earlier, he observed the third anniversary of the day that transformed his presidency and underpins his re-election campaign by attending a prayer service and presiding over a moment of silence at the White House.

"Time has passed, but the memories do not fade," Bush said in his brief radio remarks.

He applauded the courage of the Sept. 11 families and of the troops who have fought the war on terror he launched in response to the attacks.

"The terrorist attacks on September the 11th were a turning point for our nation," he said. "We saw the goals of a determined enemy to expand the scale of their murder and force America to retreat from the world. Our nation accepted a mission: we will defeat this enemy."

At St. Johns Episcopal Church near the White House, the president and the first lady, Laura Bush, both dressed in black, lit candles to open the early morning ceremony but said nothing during the service nor as they left.

In his homily, the rector, the Rev. Luis Leon, reminded Bush that "part of his role is to be chaplain to this nation." Leon also counseled that "hatred is not the answer" in responding to the terrorist attacks and asked his congregation to "pray for those who mean to do us harm."

Afterward, at 8:46 a.m. EDT, the Bushes and Vice President Dick Cheney and his wife, Lynne, presided over a moment of silence marking the minute that American Airlines Flight 11 hit the north tower of the World Trade Center on Sept. 11, 2001. Preceded by music played by a Marine band on the White House balcony and a color guard procession, the couples strode onto the South Lawn before dozens of White House staff, Sept. 11 family members and members of Congress. The foursome bowed their heads and placed their hands over their hearts as a lone bugler played taps, then silently went back inside.

As he did last year, Bush signed proclamations designating Sept. 11 as a national day of prayer and remembrance and as Patriot Day.

Bush's Democratic rival for the White House, Massachusetts Sen. John Kerry, was attending a memorial in his hometown, Boston.

Delivering the Democrats' weekly radio address, Kerry praised the spirit of the country in the days and months after the attacks. "We are one America in our prayers for those who were taken from us on September 11 and for their families," he said. "And we are one America in our unbending determination to defend our country to find and get the terrorists before they get us."

Across the Potomac River from Washington, at a ceremony at Arlington National Cemetery, Defense Secretary Donald H. Rumsfeld joined with dozens of relatives, friends and co-workers of the 184 people killed at the Pentagon on Sept. 11 to observe a moment of silent at 9:37 a.m. That was when American Airlines Flight 77 struck the nation's defense headquarters.

The innocent people on the plane and at the Pentagon will not be forgotten, Rumsfeld promised.

"The lives that were lost on September 11th have meaning. They live on as a testament to a country that is courageous, that is determined, to a people that are resilient despite great loss, and to a cause that continues until that mission is accomplished and beyond."

Bush has made the fight against terrorism the focus of his re-election effort.

"This election will also determine how America responds to the continuing danger of terrorism," he said Friday in Huntington, W.Va.

Bush's campaign has aimed to paint Kerry as indecisive in order to plant doubts about his ability to protect the nation and to persuade voters they shouldn't change course in dangerous times.

An Associated Press-Ipsos poll released Friday found that handling terrorism remains Bush's strongest issue, with 55 percent approving of the job he's done in the anti-terror battle and 43 percent disapproving. He also has a double-digit lead over Kerry on who would do a better job of protecting the country.

The only other time Bush has delivered a live radio address was on March 9, 2002, when he spoke from the Rose Garden as part of a ceremony signing an economic stimulus package into law.

Following the Sept. 11 events, Bush planned to spent the weekend at Camp David, Md. Counting his stays at his Texas ranch and his family's home in Maine, he has not spent a full day in the capital since Aug. 2.