Washington ? President Bush, who will mark the remembrance of Sept. 11 by visiting three terrorist attack sites, plans to start the observances in prayer and close them with a prime-time address to the nation.

The White House on Tuesday released details of the president’s Sept. 11 schedule, which will take him and first lady Laura Bush from a private morning church service in Washington to a moment of silence observed at 7:46 a.m. CDT at the White House. That’s the exact time that the first terrorist-hijacked jet slammed into the World Trade Center tower in New York. They will go from there to a ceremony at the Pentagon, which also was attacked on that fateful day.

The president and Mrs. Bush will then journey to Shanksville, Pa., and lay a wreath in the field where Flight 93 crashed, presumably en route to another target in Washington.

“Those who were here at the White House that day feel strongly about honoring those who gave their lives that day on Flight 93, particularly given the fact that most of us view that as saving the lives of those who were here at the White House that day,” said White House deputy press secretary Scott McClellan.

That afternoon, at 3:30 p.m. CDT, Bush will lay a wreath at ground zero, site of the World Trade Center in New York. At 8:01 p.m. CDT, he is to address the nation from New York.

Meanwhile, Tom Ridge, director of Bush’s Office of Homeland Security, said Tuesday he thinks U.S. security has improved since the attacks.

“I think we’ve made substantial progress and I think we are substantially safer than we were on Sept. 11,” he said on ABC’s “Good Morning America.”

“We still have considerable work to do in the years and months ahead,” Ridge acknowledged.

He said he knew of no “specific credible information” about any particular threat on Sept. 11.

“Obviously, this is a day that we are going to celebrate heroes. We are going to remember some extraordinary things that Americans did on behalf of one another. It’s a day of mourning,” he said.

He said he believed that “on that day, like every day since Sept. 11, America will be vigilant” and authorities “will continue to be on guard.”