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President Bush spent Sunday consumed by the two tragedies that have been the bookends of his presidency, marking the fourth anniversary of the Sept. 11 attacks before making his longest scheduled trip to the hurricane ravaged Gulf Coast (search).

As he has every year since the terrorist attacks, Bush observed a moment of silence at 8:46 a.m. EDT, the exact minute in 2001 when hijackers smashed the first passenger jet into the World Trade Center (search).

He left the White House in the afternoon on his way to New Orleans, where he was spending the night on the amphibious assault ship USS Iwo Jima (search) that is serving as the command and control center for relief efforts. The president made no comments upon his departure.

On Monday, Bush was to get a briefing aboard the ship from Coast Guard Vice Adm. Thad W. Allen, commander of the New Orleans relief efforts, and Army Lt. Russel Honore, who is coordinating military relief efforts along the Gulf Coast. The president planned to tour New Orleans in a military truck before visiting Gulfport, Miss.

It was the president's third trip to the region in the nearly two weeks since Hurricane Katrina and subsequent flooding obliterated wide swaths of the states.

The disaster has been a low point in Bush's presidency, with his job approval dipping to a record 39 percent in an Associated Press-Ipsos poll last week. Just over half of respondents said he is at fault for the slow response to the hurricane.

Democrats piled on the blame. Party leader Howard Dean on Sunday questioned why the federal government was not better prepared for Katrina after the experience of responding to the terrorist attacks.

"Sadly, the federal government's lack of preparation followed by its inept response had deadly consequences for far too many Americans in Katrina's path," Dean said in a statement. "The American people are counting on their leaders in Washington, D.C., to do better."

As Sunday's anniversary approached, Bush has linked the experience of Sept. 11 and Katrina in his speeches and his weekly radio address.

Bush's initial response to the attacks, including a grim address to the nation the same evening, boosted his job approval ratings and came in contrast to a slower recognition of the fallout from Katrina.

Bush and other administration officials marked the Sept. 11 anniversary with a simple ceremony on the South Lawn of the White House. A bugler played taps. The president, first lady Laura Bush, Vice President Dick Cheney and his wife, Lynne, stood with their hands over their hearts as they looked south over the Washington Monument and Jefferson Memorial on a beautiful sunny day reminiscent of the notorious morning four years ago.

The Bushes and Cheneys left after the brief observance, which also was attended by Cabinet members and White House staff, and did not speak. The only other sound was the roar of jet planes landing and taking off at nearby Reagan Washington National Airport in an unscripted yet eerie reminder of the attacks.

The Bushes, the Cheneys, and several Cabinet members began the day at a prayer service at St. John's Episcopal Church on Lafayette Park across from the White House. They joined the congregation in reciting prayers for the victims and survivors of Sept. 11 and the hurricane.

The Rev. Luis Leon preached that the anniversary was a time for healing and forgiveness and said the attacks have inspired a new generation to become more politically active. "If they ever wondered why they should bother to vote, then 9-11 and certainly now Katrina gave them an answer," Leon said.