Bush, Kerry trade charges over latest bin Laden warning.(Chicago Tribune)

Byline: Jill Zuckman and Mark Silva

MIAMI _ With just four days left in a presidential campaign centered on terrorism and national security, President Bush and Sen. John Kerry traded charges Friday over a videotaped warning by Osama bin Laden and over Bush's response to the Sept. 11 attacks.

Bush vowed that Americans "will not be intimidated," while Kerry said he would stop at nothing "to hunt down, capture or kill the terrorists." Kerry also blamed Bush for allowing bin Laden to escape during the Afghanistan war and said, "We are paying the price for it today."

The re-emergence of bin Laden, mastermind of the Sept. 11 attacks, adds another layer of unpredictability to an already delicately balanced race. And the video could not have come at a more momentous time for the two candidates as they tried to make a final, frenzied push for votes, summing up their most persuasive arguments and urging people to the polls.

Campaign strategists scrambled late Friday to respond to the bin Laden tape and to gauge how it …