ASHINGTON, Sept. 21 ・A senior Bush administration official said today that the "initial phase" of the assault on terrorism would be aimed at Osama bin Laden and his network in Afghanistan, but that the scale and timing of the next, broader phase had yet to be worked out.

President Bush will sign an executive order identifying specific terrorists and terror groups, and freezing assets in the United States beyond those already covered by existing measures, another senior official said. That document, the official said, would provide a road map of the terrorist groups that could be targeted over the medium term.

At the president's meeting with his security team at Camp David last weekend and in subsequent meetings in the White House, the administration official said, there was "broad agreement" that the first assaults had to be narrowly focused on the terrorists believed responsible for the attacks on the World Trade Center and the Pentagon on Sept. 11.

But the official acknowledged that there was still debate about how to conduct the next phase of the assaults, which could involve attacks on states that sponsor terrorism, unless in coming weeks they accepted Mr. Bush's invitation to come over to his side of what he has painted as a global war against terror.

"This is such a broad war on terrorism that you couldn't do everything at once," the official said.

The officials' description of Mr. Bush's immediate goals came as the Afghan leadership rejected his demand, made in a speech to Congress on Thursday night, immediately to turn over Mr. Bin Laden, his followers and any other terrorists in Afghanistan to the United States and to open their camps to American inspection.

A fourth aircraft carrier group ・the Kitty Hawk and its 40 attack aircraft and half-dozen accompanying warships ・left its base in Yokosuka, Japan, today, headed for an undisclosed location.

Two carriers are already in the Persian Gulf or Indian Ocean, and a third, the Theodore Roosevelt, left Norfolk, Va., this week for the Mediterranean Sea, and possibly points east.

At the Pentagon today, Defense Secretary Donald H. Rumsfeld signed a second deployment order, meaning that nearly 100 bomber and support airplanes are now being sent to the Persian Gulf. About 175 warplanes were already based in the gulf region, primarily to enforce the no- flight zone over southern Iraq.

More than 5,000 reservists have been called to active duty, largely for missions defending the United States, and military officials said today that planners were drafting call- ups that could far exceed the 35,000 reservists Mr. Rumsfeld has requested so far.

"I think we'll blow right past that," said Lt. Gen. Paul E. Weaver, chief of the Air National Guard. "This is going to be an extraordinarily protracted effort."

Another senior administration official said that before Monday, Mr. Bush would sign an executive order identifying specific terrorists and terror groups, and freezing assets in the United States beyond what was already restricted by the Clinton administration.

Asked about Iraq, which Mr. Rumsfeld and his aides have reportedly pressed to include on the target list, the senior White House official strongly suggested that any decisions on military action against that country would be deferred.

"The president said last night we begin with bin Laden, but it doesn't end there," the official said.

States that sponsor terrorism are to have a chance "to turn over a new leaf," the official said. Iraq, the official added, is considered unlikely to do that.

The official was repeatedly asked if the United States now held evidence specifically linking Mr. bin Laden to the two attacks on Sept. 11. Each response focused on links to Al Qaeda, the loose network of terrorists that Mr. bin Laden leads, but made only tangential reference to Mr. bin Laden himself.

This is consistent with how other administration officials have dealt with the same question. On Thursday, the deputy secretary of state, Richard L. Armitage, told a closed meeting of NATO ambassadors in Brussels that Washington was not yet prepared to provide allied nations with information pinpointing the culprits behind the attacks.

Asked at the White House today about the evidentiary trail to Mr. bin Laden, Ari Fleischer, Mr. Bush's spokesman, also talked only about Al Qaeda, but noted that both the organization and Mr. bin Laden were named in indictments for the bombing of American embassies in Kenya and Tanzania in 1998.

Mr. Fleischer suggested that there could be no equivalent of President John F. Kennedy's decision to release photographs of Soviet missiles moving into Cuba in 1962. "The challenge that the government always faces when you ask a question like that ・`provide the proof' ・is the means of providing the proof provides valuable information to those who are the objects of any potential action," he said.

"They would like nothing better than to be able to hide where they are hiding and have the United States reveal what we know and how we know it, which will make it easier for them to hide and will make it easier for them to carry out further actions, if we report our sources and our methods or how we obtain information," Mr. Fleischer said. "We're just not going to do that."

Mr. Bush met with his national security advisers today to review war planning and the administration's efforts to rally international support around the war against terrorism. He plans to speak with his national security team again on Saturday by video conference from the presidential retreat at Camp David, Md., a National Security Council spokesman said.

The deployment order that Mr. Rumsfeld signed today sends additional bombers and support aircraft, as well as maintenance crews, air controllers and security personnel, to the gulf region and Diego Garcia, a British base on an island in the Indian Ocean from which B-52 and B-1 bombers will fly, a senior Pentagon official said.

As the military continued to step up its war footing, the White House said the Defense Department would get about half of the first $5 billion installment of the $40 billion emergency package Congress passed to respond to the attacks.

The Defense Department will get $2.55 billion to upgrade intelligence and security in the aftermath of the stunning attacks, and to bring the military to full readiness. Money will also go toward repairing the damage done to the Pentagon by the hijacked airliner that smashed into it.

Mr. Rumsfeld also said he was invoking a rarely used Civil War-era law, the Feed and Forage Act, that allows the military to spend more than Congress has appropriated for clothing, fuel and medical supplies for the armed forces.

In addition, the Energy Department said today that it had suspended all shipments of nuclear materials and nuclear waste because of the terrorist attacks.

"There is a temporary hold on our shipments," said Joseph Davis, a department spokesman. "We continue to evaluate it on a daily basis."

The department did not cite a specific threat, but there is concern that such shipments are vulnerable. The material, which moves by truck, includes fuel for research reactors and waste from the production of weapons.