Bush said the loss of the space shuttle and its seven astronauts "brought terrible news and great sadness to our country."

Addressing the nation from the Cabinet Room, Bush said, "The Columbia is lost." Before his remarks, he telephoned the families of the astronauts to console them.

"These men and women assumed great risk in the service to all humanity," the president said. The astronauts knew the dangers and they faced them willingly," he said in brief remarks after rushing back to the White House from a weekend at Camp David, Md.

Flanked by two flags, Bush spoke slowly, his voice falling almost to a whisper at some points, his brows furrowed and his mouth downturned.

Quoting Scripture, the president said, "The same creator who names the stars also knows the names of the seven souls we mourn today. The crew of the shuttle Columbia did not return safely to earth but we can pray they are safely home." His eyes were glistening as he concluded.

Bush read the names of the seven astronauts — six Americans and an Israeli."All Americans today are thinking as well of the families of these men and women who have been given this sudden shock and grief. You are not alone. Our entire nation grieves with you and those you love will always have the respect and gratitude of this country.

"The cause in which they died will continue," Bush said. "Mankind is led into the darkness beyond our world by the inspiration of discovery and the longing to understand. Our journey into space will go on."

Earlier, NASA Administrator Sean O'Keefe, announcing the shuttle's demise, said he had spoken with Bush and the president had offered his "full and immediate support" to determine what had gone wrong and what to do next. O'Keefe spoke at a news conference in Cape Canaveral, Fla.

Homeland Security Secretary Tom Ridge coordinated the government response. He contacted officials in five states, including Texas, where debris from the shuttle fell.

Under an executive order signed recently by Bush, Ridge is the coordinator of all domestic incidents of this magnitude, even when terrorism is not suspected.

Ridge, working from the White House, contacted O'Keefe, Mike Brown of the Federal Emergency Management Agency, and officials at the military's Northern Command., which was created after the Sept. 11, 2001, terrorist attacks solely to defend U.S. territory. Ridge decided that FEMA, which becomes part of his department March 1, would be the lead agency for response and recovery.

Bush was briefed at Camp David on the shuttle loss. After the 90-minute drive from Maryland's Catoctin Mountains, the president stepped out of a sports utility vehicle and strode to the Oval Office in a cold drizzle. Later he went to the White House residence with chief of staff Andrew Card, looking down at his feet as they walked along the colonnade.

"There is no information at this time that this was a terrorist incident," said Gordon Johndroe, spokesman for the Homeland Security Department. "Obviously the investigation is just beginning, but that is the information we have now."

FBI spokeswoman Angela Bell also said there was no indication of terrorism. She said the FBI would have a tangential role in the investigation, mainly assisting in evidence recovery.

Another official said no threat had been received against the flight, and the shuttle, at an altitude of about 203,000 feet over north-central Texas when it lost contact, was out of range of surface-to-air missiles.

A senior law enforcement official, also speaking on condition of anonymity, said there had been some intelligence that raised concerns about a previously scheduled flight of Columbia, which was to have carried the same crew. The intelligence, related to Israeli astronaut Ilan Ramon, was termed not credible, but the flight was postponed for other reasons. There had been no troubling intelligence regarding this flight, officials said.

Vice President Dick Cheney was briefed this morning in Texas, where he was spending the weekend hunting, said spokeswoman Jennifer Millerwise. She said he was not in the part of Texas where the shuttle was lost.