The Associated Press

WASHINGTON, D.C. — The U.S. government raised its threat level to the highest level for commercial flights from Britain to the United States early Thursday in response to a reported terror plot in London and also stepped up the general level for all flights within the U.S. or entering the country.

"We believe that these arrests (in London) have significantly disrupted the threat, but we cannot be sure that the threat has been entirely eliminated or the plot completely thwarted," said Homeland Security Secretary Michael Chertoff in announcing that the threat level for flights from Britain to the United States has been raised to the highest "severe or red" level.

"To defend further against any remaining threat from this plot, we will also raise the threat level to High, or Orange, for all commercial aviation operating in or destined for the United States," Chertoff said.

A statement issued by Chertoff said "currently, there is no indication ... of plotting within the United States."

"Consistent with these higher threat levels, the Transportation Security Administration is coordinating with federal partners, airport authorities and commercial airlines on expanding the intensity of existing security requirements," Chertoff said.

"Due to the nature of the threat revealed by this investigation, we are prohibiting any liquids, including beverages, hair gels, and lotions from being carried on the airplane."

He said the changes take effect at 4 a.m. local time across the United States and will be undated as warranted.

Chertoff said travelers in the United States "should also anticipate additional security measures within the airport and at screening checkpoints."