As the clock nears midnight on Dec. 31, officials at home and abroad will undertake what is expected to be the largest law-enforcement effort in United States history.
From small-town cops to international agents, one goal will predominate: Prevent the terror and mayhem that many people predict as the calendar turns 2000.
Such efforts are not new to US law-enforcement agencies - they have been battling terrorists intensely for a decade.
What is new is the perceived end of the millennium - a time when right-wing religious groups have said they would help trigger Armageddon, when some scientists say Y2K computer problems could affect nuclear weapons, and when the world's leading terrorist, Osama bin Laden, has predicted the beginning of a century of Islam.
"The options for terrorists are immense.... To guess where and when it will happen is impossible," says Yossef Bodansky, who heads a congressional panel on terrorism and unconventional warfare. But "the commitment by law enforcement ... is great."
As if to prove their confidence in American defense, several US leaders have promised to be in public at the big moment. President Clinton plans to attend a party on the National Mall in Washington. And, says New York City Police Commissioner Howard Safir, "I will be in Times Square at 12 midnight ... and my family will be standing with me right under the ball."
For terrorists - who thrive on attention - the timing of a midnight blast could not be better. The media will be running full tilt, and disaster images could be spread worldwide in seconds.
While officials have mentioned New York City, Washington, and Seattle as possible terrorist targets, experts say a strike could occur in a less obvious place. That was the case in 1996, when Atlanta's Olympic Park, rather than a more prominent Olympic venue, was bombed. Some high-profile locations, such as the United Nations, will close Dec. 31 as a precaution.
Attacks today have the potential to be deadlier than ever because of biological and chemical weapons, says Patrick Cronin, a terrorism expert at the US Institute for Peace. "There are bound to be some mess-ups that could be quite costly."
Already, US officials have brought a storm of media attention by releasing information about terrorism attempts they may have foiled. Fourteen suspects were caught in Jordan. The FBI warned of suspicious packages sent from Germany. And three internationals were recently arrested and linked to terrorism upon entering the US from Canada. But, if anything, these people may have been small pieces of a larger plot, analysts say.
Law-enforcement officials will counter the threat with an unprecedented preventive effort. At the top of the pyramid is Richard Clarke, the National Security Council terrorism czar who will coordinate domestic and international efforts. He will be backed by city and state police departments, US border guards, the Pentagon, the Justice Department, the State Department, the FBI, the CIA, and other agencies.
All points of entry into the US - land, sea, air - will continue to be carefully scrutinized.
On the local level, most big-city police forces will be running at full strength and, sometimes, altering celebration plans:
*In New York City, 37,000 out of 40,000 officers will be up and about, including 8,000 in the five-block Times Square area, where manhole covers will be welded shut and six police helicopters will hover overhead.
*In Phoenix, the entire force of 3,600 sworn and civilian officers will work shifts from 6 a.m. Dec. 31 through New Year's Day.
*Seattle canceled its New Year's Eve celebration below the Space Needle.
*Saint Paul, Minn., decided to hold New Year's Eve a day early - complete with a faux countdown to midnight.
*At Pasadena's Tournament of Roses Parade, "security will be visible everywhere," says Police Commander Mary Schander, with 1,000 officers on foot and motorcycles along the five-mile route.
Because the possible threats against the US are myriad, so too are the measures taken to prevent them.
The Federal Emergency Management Agency, will, for the first time ever, have its 10 regional centers open all at once.
US and Russian defense officers will sit side-by-side Dec. 31 at a missile-warning center in Colorado Springs, Colo., in case a radar glitch makes it seem as if missiles are approaching either nation.
Other Y2K computer concerns appear to have been alleviated by billions of dollars in preparations.
If a threat does exist within US borders, it may be extremist groups bent on kicking off Armageddon at the close of the 1900s. Some groups, such as those that equate the federal government to Satan, may try to provoke a government crackdown and parlay it into an uprising.
"Militias, adherents of racist belief systems such as Christian Identity and Odinism, and other radical domestic extremists are clearly focusing on the millennium as a time of action," says an FBI report.
Among the most difficult attacks to defend against, analysts say, are those against US targets abroad. The State Department has urged citizens to be cautious and avoid large crowds - especially in the Mideast.
Much attention has focused on Mr. Bin Laden, the Saudi exile who has declared war against the US and is accused of orchestrating last year's attacks on US embassies in Kenya and Tanzania.
Thought to be in hiding in Afghanistan, he is eager to demonstrate that he can "reach out and touch wherever he wants whenever he wants," says Mr. Bodansky.
So far the US war on terrorism has been largely successful.
According to Mr. Cronin, the US has been the site of only two confirmed international terrorist attacks in the 1990s - the 1993 World Trade Center bombing in New York (even though the immediate perpetrators lived in the US) and a 1992 attack on Iran's United Nations mission.
Whether or not the US gets hit by a terrorist strike this weekend, analysts say the rolling of the clocks will signal neither the beginning nor end of an ongoing war.
Says Cronin: "On Jan. 2, 2000, terrorists will still be a real threat."
*Ron Scherer in New York and Stephanie Cook in Boston contributed to this story.
(c) Copyright 1999. The Christian Science Publishing Society