President Bush says U.S. intelligence officials are hunting those responsible for Tuesday's terrorist attacks in New York and Washington. Search and rescue teams are still searching the rubble of the destroyed World Trade Center.

President Bush says the U.S. government will be open for business Wednesday morning. In a nationwide address, he said the American people will not be cowed by terrorism. "These acts of mass murder were intended to frighten our nation into chaos and retreat, but they have failed," he said. "Our country is strong. A great people has been moved to defend a great nation. Terrorist attacks can shake the foundations of our biggest buildings, but they cannot touch the foundation of America."

Thousands of lives were lost when terrorists hijacked commercial airliners and smashed them into the World Trade Center in New York and the Pentagon outside Washington. President Bush says these acts of "mass murder" will not go unpunished. "The search is underway for those who were behind these evil acts," he said. "I have directed the full resources of our intelligence and law enforcement communities to find those responsible and to bring them to justice. We will make no distinction between the terrorists who committed these acts and those who harbor them."

The president placed U.S. military forces around the world on their highest state of alert. Nuclear power plants and nuclear fuel facilities are also the subject of extra security precautions. All U.S. air traffic has been grounded until at least midday Wednesday.

Rescue teams are continuing their search for survivors in the wreckage of the World Trade Center. Those teams include engineers to help stabilize damaged buildings and dogs trained to search for people trapped in the rubble.

Stock exchanges will remain closed Wednesday. The U.S. Central Bank says it is ready to pump extra money into the economy to prevent the violence from pushing an already struggling economy into recession.

The European Commission and EU foreign ministers Wednesday hold emergency meetings to assess the situation. Several world leaders, including Russian President Vladimir Putin and South African President Thabo Mbeki issued calls for international cooperation to fight terrorism.