By DAVID ESPO
AP Special Correspondent

WASHINGTON - American pilots bombed targets in Afghanistan day and night Tuesday, and President Bush declined to say whether ground troops would be added to the campaign against terrorism. The United Nations listed four security guards as civilian casualties of the military bombardment.

"With the success of previous raids, we believe we are now able to carry out strikes more or less around the clock as we wish," Defense Secretary Donald H. Rumsfeld said at the Pentagon.

Bush, asked about the progress of the military operation, declined when asked about the possible use of ground forces. "I'm not going to tell you," he said.

Bush coupled his statements with a stern lecture to members of Congress. He said he had recently restricted the flow of information to many lawmakers because at least one had failed to keep classified information confidential.

"I understand there may be some heartburn on Capitol Hill," he said. "But I suggest if they want to relieve that heartburn they take their position very seriously."

Bush spoke with German Chancellor Gerhard Schroeder at his side after talks in the White House. Germany is one of several nations that Bush has mentioned previously as willing to participate in military operations against terrorist targets in Afghanistan.

With federal agencies warning of the possibility of further terrorist strikes, Bush said "we're on high alert on the governmental level. But the American people should go about their business."

Asked whether he still wants Osama bin Laden dead or alive, as he once remarked of the suspected mastermind behind the Sept. 11 attacks, Bush smiled. "I want there to be justice," he replied.

The president said he considered the military operation thus far to be a success. "The skies are now free" over Afghanistan, he said.

He spoke a few hours after Rumsfeld and Gen. Richard Myers, the chairman of the Joint Chiefs of Staff, offered an optimistic assessment of two nights of bombing. "We feel like we have, essentially, air supremacy over Afghanistan now," said Myers.

Rumsfeld, sharing the podium at the Pentagon, said the United States was also encouraging dissidents inside Afghanistan to "heave the Al-Qaida and the Taliban leadership...out of the country."

Administration officials declined to specify the targets of the renewed attacks. But anti-aircraft fire could be heard in the Afghan capital, Kabul, and Taliban officials reported bombs falling around their headquarters in Kandahar and the northwestern city of Herat.

In Florida, the FBI continued its investigation into the death of one man from anthrax, and the exposure of a co-worker to the deadly disease.

"It remains a situation of concern with the federal government," said White House spokesman Ari Fleischer, as officials offered antibiotics as a precaution to hundreds who worked in the same building as the two men. Fleischer added, however, that "it's not unusual at times like this for false alarms to go off."

At the Pentagon, Rumsfeld said the United States had no independent verification of the reported deaths of the U.N. workers, or whether they might have died after being hit by anti-aircraft fire.

"Nevertheless we regret the loss of life," he said.

"If there were an easy way to root terrorist networks out of countries that harbor them, it would be a blessing, but there is not," he added.

The defense chief added that some ground forces "were targeted in the north" of Afghanistan, where the forces of the northern alliance are arrayed against them.

The bombing marked the third straight night of attacks by American-led forces. But even before night fell, pilots flew strikes sporadically throughout the day, a sign of increased confidence that whatever air defenses the ruling Taliban regime possessed had largely been suppressed.

Taliban officials said Osama bin Laden, the suspected mastermind behind the Sept. 11 terrorist attacks in New York and Washington, had survived the American assault.

Abdul Salam Zaeef, the Taliban envoy to Pakistan, told reporters the United States had spurned Afghanistan's request for evidence of bin Laden's involvement. "America is sending warplanes, bombs and cruise missiles in place of evidence," he said.

Administration officials said there was proof enough _ even before bin Laden's videotaped message released on Sunday praising the attacks that killed thousands and taunting America as a nation afraid.

One day after former Pennsylvania Gov. Tom Ridge was sworn in as the nation's first director of homeland security, the administration was adding new top-level officials to the effort. Administration sources said Richard Clarke, who heads the government's counterterrorism team, will direct the security effort for the nation's information systems. Retired Gen. Wayne Downing was tapped to work with military and intelligence resources, these officials said.

U.N. officials confirmed the deaths of four security guards for a mine-clearing program in Afghanistan, the first independent verification of civilian casualties in the U.S.-led war effort.

U.N. spokeswoman Stephanie Bunker said the four had been spending the night in their office, on the edge of Kabul, and in close proximity to a radio transmission target that was a target of bombs.

"It was assumed they were safe where they were," said Bunker, speaking from the Pakistani capital of Islamabad. "Otherwise they would have been relocated for sure."

In an appeal to the United States, she said, "People need to distinguish between combatants and those innocent civilians who do not bear arms."

"It's inevitable there will be mistakes that take place in a situation where the lines remain unclear," said Sen. John McCain, R-Ariz. McCain, who made his comments in an interview on ABC's "Good Morning America," was a Navy pilot during the Vietnam war, and an American prisoner of war.

Pilots flying from the USS Enterprise in the Arabian Sea returned from Monday night's bombing runs with unused live bombs, the carrier's captain said.

But Rumsfeld said: "We're not running out of targets, Afghanistan is. And I would add, that they are emerging as we continue."

American officials have identified bin Laden as the leading force behind the Sept. 11 attacks that killed more than 5,000 people at the World Trade Center, the Pentagon and in a plane crash in the southwestern Pennsylvania countryside.

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