U.S. officials have kept the information secret, and Homeland Security Secretary Michael Chertoff said today on ABC News' "This Week with George Stephanopoulos" that the United States did not have "have any specific credible evidence that there's an attack focused on the United States at this point."
As ABCNews.com reported, U.S. law enforcement officials received intelligence reports two weeks ago warning of terror attacks in Glasgow and Prague, the Czech Republic, against "airport infrastructure and aircraft."
The warnings apparently never reached officials in Scotland, who said this weekend they had received "no advance intelligence" that Glasgow might be a target.
Homeland Security Secretary Chertoff declined to comment specifically on on the report today, but said "everything that we get is shared virtually instantaneously with our counterparts in Britain and vice versa."
Unlike the United States, officials in Germany have publicly warned that the country could face a major attack this summer, also comparing the situation to the pre-9/11 summer of 2001.