Massive Security Forces Readied in Rio : Summit: National, foreign and U.N. agencies are participating in effort to protect world leaders at the conference.

A massive, multinational security operation is gearing up to protect the 116 presidents and prime ministers expected to attend the United Nations Earth Summit, one of the largest gatherings of world leaders in history.

Brazilian army troops and uniformed police are intensifying vigilance in key areas of Rio, as federal plainclothesmen watch the borders and airports for suspected terrorists. Federal police also are working with U.N. security personnel and some 150 foreign security agencies, including the U.S. Secret Service.

President Bush, who will be one of the most closely guarded participants in the summit, was to arrive early Friday. It is an open secret that he will have rooms in the seaside Sheraton Hotel on the southern side of Rio. Officials would not say whether Bush would be moving around by helicopter or motorcade.

If or when Cuban President Fidel Castro might arrive has been kept secret, reportedly for security reasons.

Delegates from 178 countries are participating in the U.N. Conference on the Environment and Development. Joe Sills, conference spokesman, said that 116 heads of state or government have confirmed that they will attend the summit in its last days, Friday and Saturday.

Many already have trickled in, and the trickle will become a flood today. Sills said security logistics and the size of the conference present “a difficult and delicate situation.” “There is immense pressure,” he told reporters Wednesday.

Starting today, several major streets were to be blocked off for official motorcades, adding to the normal turmoil of Rio traffic. The leaders will travel on routes that pass below hillside slums, beside high-rise apartments, through tunnels and over bridges.

“The screening of the whole route will be done by the army with detectors and other resources,” Rio traffic engineer Tulio Andrade said in a newspaper interview published Wednesday.

The road to the summit site, several miles south of the city, will be open only to authorized traffic, including cars carrying thousands of reporters. Air space over the site has been closed except to authorized flights. Police and military helicopters will conduct aerial surveillance; they will not be used by most of the visiting leaders because their hotels do not have landing pads.

Federal police chief Romeu Tuma said the international police information network Interpol is coordinating special intelligence efforts to monitor groups around the world that might try radical action at the conference. “That system is functioning 24 hours a day,” Tuma said Wednesday. So far, he told a press briefing, “there is no information that any group wants to act during the event.”

He said strict security measures are being taken at the hotels of official delegations, in neighborhoods they will travel through and around Rio Centro, the convention and exhibition complex housing the summit. He said more than 1,000 federal police are working on summit security, and, according to press reports, 35,000 uniformed police and army troops are assisting.

Armored combat vehicles are parked at scattered locations. One is near Rocinha, a large hillside slum that overlooks a main motorcade route.

Tuma said an important security goal is to prevent any disturbance, but he added that the security system “was mounted without any spirit of repression.” He said police are still looking for gang members who killed two federal policemen in a slum before the environmental conference began. “They are being pursued within the law and this will not stop,” he said.

Times staff writer Rudy Abramson contributed to this story.