The U.S. government is urging Americans to be vigilant about suspicious activity after British police defused a bomb in downtown London, but officials said they saw no potential terrorist threat in the United States ahead of next week's Fourth of July holiday. The Department of Homeland Security said in a statement that it was in close contact with state and local authorities around the nation but had ``no specific credible information suggesting a threat to the homeland at this time.'' ``At this time we are characterizing this as a localized incident in London,'' DHS spokeswoman Laura Keehner said. ``We encourage the public to enjoy the upcoming holiday but ask, as always, that they be vigilant and report suspicious activity to authorities,'' she said. FBI spokesman Richard Kolko said there were no related threats in the U.S. President Bush was briefed on the incident by national security adviser Stephen Hadley in Maine, where the president is at his family's home to meet Sunday and Monday with Russian President Vladimir Putin. ``We commend the British security services for their action today. U.S. officials are in contact with their U.K. counterparts and will continue to monitor the situation,'' said Gordon Johndroe, a spokesman for the National Security Council. The bomb near Piccadilly Circus was powerful enough to have caused ``significant injury or loss of life'' _ possibly killing hundreds, British anti-terror police chief Peter Clarke said. The London threat comes at the same time as U.S. counterterrorism authorities are worried about terrorist activity in the tribal areas of Pakistan. The official noted al-Qaida's continued presence there.
