President Bush says Congress must safeguard classified information it receives while investigating what U.S. officials knew about terrorist threats before September 11. The president's criticism follows the disclosure that intelligence officials intercepted two messages on September 10 warning that something was going to happen the next day.

White House spokesman Ari Fleischer says the president is concerned about what he calls "the inappropriate disclosure" of information that could interfere with the nation's ability to fight terrorism and may undermine national security.

"The information that was leaked is alarmingly specific and the president does have very deep concerns about anything that would be inappropriately leaked that could in any way endanger America's ability to gather intelligence information," he said.

The warning follows reports that the National Security Agency intercepted two Arabic-language messages on the eve of the attacks, one of which said "Tomorrow is zero hour."

The disclosure is believed to have been leaked from classified testimony before a Congressional committee.

Vice President Dick Cheney telephoned the committee co-chairs Thursday morning to complain about the leaks. Mr. Fleischer says the Administration is confident that Congressional leaders will deal with the problem and he says there is no plan to restrict further testimony.