U.S. President George W. Bush vowed swift revenge on the terrorists that unleashed the deadly attacks on New York and Washington Tuesday, saying "the United States will hunt down and punish those responsible for these cowardly acts."

Speaking via tape from Barksdale Air Force Base, La. Tuesday before 1 p.m. EDT, Mr. Bush said the government has taken all appropriate security precautions to protect the American people.

Mr. Bush said the U.S. military had been put on "high alert status" and said he had taken security precautions to ensure the functioning of the U.S. government.

The remarks were part of the President's second official statement following the attacks, which began early Tuesday morning, around 8:45 a.m. EDT.

Mr. Bush spoke briefly from Florida during the immediate moments after the planes crashed into the World Trade Center, calling the moves an apparent terrorist attack.

Mr. Bush left Barksdale Air Force Base for Nebraska's Offutt Air Force Base at 1:37 p.m. EDT. Mr. Bush was at Barksdale after departing from Florida earlier Tuesday. U.S. officials said he would fly back to Washington, D.C. later on Tuesday night and was expected to make another public statement at that point.

"The resolve of our great nation is being tested, make no mistake, we will show the world we will pass this test," he said. "This is a very difficult moment for America," Mr. Bush said.

"Today we've had a national tragedy," Mr. Bush.

Mr. Bush said he has spoken to Vice-President Dick Cheney as well as the governor of New York and the director of the FBI.

The full resources of the federal government, he said, will go to help the victims and their families.

"Terrorism against our nation will not stand," he said, calling for a moment of silence. "May God bless the victims, their families and America."

This is the second attack on the World Trade Center, which was struck by a bomb in 1993.