"When it is lowered, and I'm confident it will be, then there will be an appropriate explanation at the time," he said.
Ridge defended the Bush administration's decision last week to increase the level to the second from the top on a color-coded scale of five, even though the government later determined that some of the information which led to the upgrading was likely fabricated.
"The decision to raise it to orange was not based on one or two sources," he said in a broadcast interview.
A senior administration official, speaking on condition of anonymity, said Saturday that the end of the hajj — the Muslim pilgrimage to the holy Mecca — was causing officials to consider seriously lowering the threat level.
Ridge will present a "Ready Campaign" Wednesday encouraging the public to have a communication plan with their family, to prepare an emergency supply kit and to "stay alert on a day to day basis."
"Terrorists give us a choice. We can either be afraid, or we can be ready," said Ridge.
Ridge also said U.S. intelligence officials were evaluating a new tape, purportedly of Osama bin Laden saying American war plans against Iraq are part of a broader plot against Muslim nations.
There has been some information about a second bin Laden tape "swirling around within the intelligence community for the past couple of days," he said. "Obviously we haven't authenticated it, but again the message is consistent: The values of the West are anathema to these people. If you don't believe, you're an infidel."
While the release of statements from bin Laden have foreshadowed past terrorist attacks, Ridge said he saw no "trigger" in the latest tape.
"But there is no rhyme or reason to when they attack," Ridge said. "Ultimately they attack when they are ready."
The speaker on the tape said the goal of any U.S. war against Iraq would be to alter the map of the Middle East to benefit Israel. The recording appeared to be the same 53-minute tape of which a few excerpts were released Thursday by the British-based Islamic Al-Ansaar news agency. It began appearing in full Sunday on Islamic-oriented Web sites. Al-Ansaar had said it acquired the tape from a seller who advertised it over the Internet.
Ridge also said intelligence operatives were keeping tabs on the 20 to 40 people in the United States who have trained in al Qaeda camps in Afghanistan, but said not enough evidence had been gathered to take them into custody.
"We know that they've got a rather substantial network. But this is a country that operates under the rule of law. There are restrictions to what we can do and when can do it," he said. "When the rule of law and the burden of proof gets us to where we can take action, then I assure you we will."
Ridge declined to comment on the specifics of a report in Newsweek magazine saying the CIA believes that Iraqi President Saddam Hussein could be planning to launch a terrorist attack on the United States, using weapons of mass destruction.
The CIA analysis, the magazine reported, found a 59 percent probability an attack would occur before the end of March, but only a 6 percent chance such an attack would never occur.
"This is a rogue regime that has chemical, biological weapons, is trying to develop nuclear weapons and has means of delivery," Ridge said. "That's the reason this individual needs to be disarmed. How they rate and how they give odds on whether or not an attack will occur, I'm not familiar with the methodology."