President Bush has strongly condemned the terrorist attacks in London Thursday, saying he and other world leaders will not yield to terrorists.
Mr. Bush expressed his condolences to British Prime Minister Tony Blair and the people of London as he spoke to reporters outside the Group of Eight summit in Scotland.
The president says he had spoken with the U.S. Department of Homeland Security to ensure "extra vigilance" in the United States.
White House officials say Mr. Bush will return home as planned on Friday.
Meanwhile, the Homeland Security Department announced it has raised the threat alert level for buses, subways and trains to "high."
Homeland Security Secretary Michael Chertoff said the change does not apply to airlines.
And he says the overall threat level will remain at "elevated."
Also today, U.S. Secretary of State Condoleezza Rice ordered American embassies around the world to review their security procedures.