As dignitaries arrive for funeral, security tightens

ROME -- The Italian military has positioned antiaircraft batteries around the city. Police bomb squad units are burrowing through ancient Roman aqueducts and modern sewer systems searching for explosives. Snipers have staked out the rooftops around the Baroque grandeur of St. Peter's Basilica. And fighter jets on tarmacs are set to scramble.

Tomorrow's funeral Mass for Pope John Paul II -- expected to be the largest gathering of world leaders ever and one of the largest gatherings of mourners in history -- has presented Italian and Vatican officials with an unprecedented security challenge as the ancient rituals of the burial of a pope meet the post-Sept. 11 threat of terrorism.

Authorities say they are expecting as many as 4 million pilgrims, mourners, and tourists to be present in Rome for the funeral. City authorities declared last night that mourners at the end of the line to view the pope's body were in for a 24-hour wait, so they closed the queue and said no additional pilgrims would be permitted to join it.

Security specialists call the massive crush of people a ''target-rich environment" for a terrorist, especially with the presence of 200 world leaders, including President Bush. There have been no reports of threats, but the precautions are nonetheless intense.

Bush arrived in Rome yesterday and went immediately to St. Peter's Basilica, along with his wife, his father, and former President Bill Clinton, to pay last respects to the pope, who died Saturday after an extraordinary 26-year reign.

As they knelt and prayed, the heavy police security around St. Peter's Square tightened, a glimpse of the massive security presence that will begin to take shape over the next 24 hours.

For the church hierarchy, such a militarized counterterrorism strategy cuts against the grain. The Holy See has always frowned on weapons of any kind being carried inside Vatican City.

The Vatican has its own private army of Swiss Guards, who still dress in 15th-century uniforms of red, yellow, and blue. They are responsible for the pope's safety, but the long pikes they carry would not do much to defend against a serious attack.

''Two hundred world leaders, millions of people all gathered together in one country which after America and Britain is the most attractive target for terrorism in the Western world. If you put all those ingredients together, you have a nightmare in terms of security," said Andrea Nativi, a security analyst for the Italian government and editor of a monthly journal called Italian Defense Review.

The world leaders will begin to assemble here today, and this phase of ''moving them into place," as Nativi put it, presents a higher security risk than the moment at which they are all expected to be gathered in St. Peter's Square for the funeral.

''We are concerned, I will say. Not frightened. But the potential for a terrorist to exploit this situation is very considerable," added Nativi.

Bush is traveling with former Presidents George H.W. Bush and Clinton, Laura Bush, and Secretary of State Condoleezza Rice. They knelt together and prayed in a front pew observing the body, which will be laid to rest in a crypt beneath the basilica after the funeral service.

Italy has not been a direct target of international terrorism since the 1980s, when the Italian Red Brigades struck with regularity and a Palestinian militant group carried out a deadly attack at the airport. But the Italian government's support for the US-led war in Iraq and the pope's symbol as the most visible Christian leader in the world have made the funeral a high-risk target.

While security concerns and logistics were consuming the Italian government, the Vatican was focusing on the ritualized chain of events that will take place during the pope's funeral, his burial, and the aftermath when the cardinals will gather to elect a new pope.

The College of Cardinals met yesterday and set April 18 as the date for the start of the conclave to elect a successor to John Paul, as the Vatican made final arrangements for the funeral.

During their meeting yesterday, the cardinals heard a reading of the pope's will, which is to be published today in Polish -- the language in which the pope drafted it -- and in Italian. Cardinal Francis E. George, the archbishop of Chicago, told reporters that the will ''is a spiritual testament" and that ''especially at the end, it's very moving."

Last night, pilgrims continued to stream forward through a maze of barricades and side streets, some waiting as long as 20 hours to pay their respects to John Paul, who has been lying in state in the basilica since Monday afternoon. They have filed past the pope's body at a rate of more than 15,000 people per hour, according to calculations by the Italian civil defense department. The city provided hundreds of portable toilets, and volunteers handed out bottled water.

At 10:30 p.m., police moved the barricades to shut down the line, saying Vatican officials could not permit any more people if it was going to have time to clean the streets and prepare the basilica for the funeral Mass. Rosa Liva, 35, an immigrant to Italy from Kerala, India, who works as an au pair with a family in Rome, was stopped by police at the barricades and turned away.

''I am so sorry because I work all day and I really wanted to see this," she said.

She paused and then added, ''I will still wait; it is good just to be here."

Globe correspondent Sofia Celeste contributed to this report, and material from the Associated Press was also included.