Soviet leader Mikhail Gorbachev will view a sanitized and sealed Washington next week from the inside of an armored Soviet Zil limousine, flown in for his safety in a secure cargo plane. During the summit, he will travel from one heavily guarded site to another in a protective cocoon, fashioned by a half-dozen law enforcement agencies -- including his own KGB -- in the most well-secured Washington in history.

Nothing will be left to chance -- a word the Secret Service despises. Sealed manhole covers will sit above sewers searched by special teams. Bomb-sensitive dogs will be all around, sniffing even the television camera to be placed atop the Washington Monument. About a dozen black Soviet limousines, imported for the occasion, will carry a Soviet entourage protected, in the language of the Secret Service, by "360-degree security."

"There's going to be tight, tight, tight security," said one source familiar with the preparations. " . . . Depending on the side of the table you're sitting on, this is either the most important man in the world or the second most important."

Security will be so tight that President Reagan will not realize his long-held wish that Gorbachev see America. Indeed, the powerful world leader, who Reagan believes would be greatly affected by the sights, will see less of Washington than the typical tourist from Akron. Other than his trip from Andrews Air Force Base in Prince George's County, Gorbachev's movements, as announced, mostly will be bounded by 22nd Street on the west and his own 16th Street embassy on the east. One proposed jaunt -- to the U.S. Capitol -- was canceled in a political huff.

Instead of the grandeur of the Reflecting Pool or a real Washington neighborhood, Gorbachev will see America's inner sanctums, places such as the Oval Office where few Americans can venture.

Nor will Washington see him. Except for his speeding car, the best view of the general secretary will be on TV.

Top U.S. and Soviet officials are "antsy and nervous" about the safety of their nations' leaders, said one law enforcement official coordinating security. "The word's come down, 'We don't want anything to happen at this event . . . You can't afford to make a mistake.' "

The Secret Service and the KGB, the Soviet intelligence agency whose duties include guarding the general secretary, have labored day and night over the past month -- in a kind of summit before the summit -- to settle the intricate security arrangements.

The process has been relatively smooth. But negotiations at times can be as delicate as the arms control talks themselves, reflecting the two sides' vastly different politics and cultures.

William Corbett, spokesman for the Secret Service, the agency that protects the president and top foreign leaders, said the event is "a logistical nightmare . . . . There are a lot of last-minute changes and adjustments . . . . We always second-guess ourselves. If we don't, someone else will."

It will be different from the summits of the past.

There will be no trip from the airport with the president in an open Lincoln, as there was for Nikita Khrushchev in his 1959 visit here. In 1973, Leonid Brezhnev and Richard Nixon greeted schoolchildren on the White House lawn -- but this time security experts say that if anything like that occurred, the tots would be routed through metal detectors.

From the security professionals' point of view, it is quite a different world from 1973. "Anwar Sadat has been blown away," said a former White House official familiar with security matters. "The pope and the president have been shot . . . . The level of terrorist tactics has definitely increased."

Still, the tight security will be discreet in many ways.

Most of Washington, D.C., will go about its workaday life, and there will be little disruption to most people's schedules, except for traffic jams caused by the barricading of some downtown blocks.

Law enforcement officials want to keep their security procedures as unobtrusive as possible -- not a simple task when 135 KGB agents join the mass of U.S. security agents stationed around the city.

"We want to do a good job of providing security, but this is a nation of free people," said Assistant D.C. Police Chief Isaac Fulwood, overseeing the department's ambitious summit planning. "We've got to be careful not to abridge people's rights or to overreact."

The Secret Service shares this view. On details protecting the president, some agents carry Uzi submachine guns, but are required to keep them hidden unless there is immediate danger.

The preparations for Reagan's 1985 inauguration were the most security-conscious in the city's history, and included 9,000 law enforcement officers from a range of agencies. This one will be even bigger, and the preoccupation with security will be more intense, government officials said.

Representatives of all the agencies involved -- from U.S. Park Police to the State Department -- started meeting soon after the Oct. 30 announcement of the summit. They went over every scenario, every escape route, every fallback plan, "worst-casing it" in their lingo. They have met about 50 times in the last three weeks alone.

More than 100 Secret Service employes have been working full time for weeks attending to a myriad of details, from securing the buildings along planned motorcade routes to checking the backgrounds of employes at the Madison Hotel, where many Soviet officials will stay. At some point before the Soviets move in Monday, Secret Service teams will sweep through the hotel and "turn it inside out" -- checking for bombs and any suspicious items, one official said. Then they will control access completely, aware of everything that goes in or out, "including the garbage," one source bragged.

The agents also have focused on the hospitals to be visited in the event of an emergency. They have checked the backgrounds of doctors and other staff members.

"Sometimes you start to squeeze your head and say, 'I thought I'd thought of everything, but here's something I hadn't,' " Secret Service spokesman Corbett said. "It's a stressful job. It seems there's no end to the problems that arise."

Fulwood, who has been working 16-hour days, said his officers are so primed for the event that they feel like jittery football players on the eve of the Super Bowl. "Monday, come on and get here."

When it comes, there will be helicopters whirring over the motorcade routes, "countersnipers" poised on downtown rooftops, police infiltrators looking out for trouble among the demonstrators, battalions of officers stashed discreetly in government buildings, and tight formations of Secret Service agents surrounding their "protectees" inside secure "buffer zones." The whole affair is coordinated with split-second timing by a 24-hour command center deep inside the White House.

One thing that will be missing from the security extravanganza will be the Soviets' helicopter. Earlier, they had sought to bring one by cargo plane to ferry their leader around Washington. But U.S. security officials put the kibosh on that. They were unenthusiastic about a camera-laden chopper zooming over the capital's most sensitive installations.

The helicopter seems to be one of the few requests by the Soviets that U.S. officials did not grant. The two sides have worked together well, in sync because both have the same interest: maximum safety and minimum risk for their leaders.

The two nations also share a mission that is distinct from protection in the usual sense -- they are committed to preventing embarrassing incidents. With 7,000 journalists chronicling even the tiniest event, however symbolic, these agencies are expected to prevent anything that could cast their leaders in a negative light -- from egg-throwing and paint-splattering to a sit-in disrupting a motorcade.

But the KGB and Secret Service have different approaches to protection borne of their different political cultures.

"The KGB will be more aggressive," said a former senior security official. "They are not used to an environment with so much freedom . . . . They're not used to demonstrations, people shouting at their leader. In their culture, it is practically unheard of for citizens to demonstrate. They will be uneasy."

He recalled that during Brezhnev's 1973 visit to Nixon's San Clemente compound, KGB agents were frightened by protesters clamoring at the gates. The Soviets asked, he said, "Why do you have these? Can't you stop it?" The Americans answered, "It's our culture and our laws."

The two sides differ on the same point 14 years later -- and the answer is still the same. The Americans insist the summit entourage must bear the presence of rowdy protesters, even within earshot.

In the past, the two nations' agents have found themselves practicing a subtle one-upmanship, both in jest and in seriousness, trying to test each others' limits. U.S. officials who have dealt with Eastern Bloc agents recall squabbling over a number of security issues, both real and symbolic -- everything from the visitor's itinerary to whose car he uses in motorcades.

In Nixon's 1974 trip to Moscow, one security official recalls a standoff at the airport. It had already been determined that Nixon would travel in Brezhnev's car when the two leaders were together, but the rules of the game demanded that a Secret Service agent accompany him.

But this time, a KGB general suddenly informed the lead agent his place had been taken in the crowded car. He would have to follow. The agent argued to no avail. Just as the car was about to pull away, the agent jumped into the full front seat -- and onto the general's lap. A participant recalled the general as "a little guy" and the agent as "pretty big."

The one-upmanship is not confined to the superpowers. U.S. law enforcement agencies themselves often practice a type of macho infighting, declining to share information with their counterparts, officials said. While participants say this summit planning has gone relatively smoothly, it represents an improvement from the past.

"There's always a little bit of friction," said Robert Klotz, a former D.C. deputy police chief who handled many such events for the department and is now a security consultant. "It's a nightmare if (bureaucratic) egos start getting going."

U.S. agencies have been cooperating for weeks in collecting intelligence about potential troublemakers, sources said. It is an inexact science, trying to psychoanalyze from afar who might try to harm the leaders. The Secret Service has a staff of psychologists studying the propensity for violence of hundreds of persons whose cases are included in their 40,000 computerized files. Those considered most dangerous are known as "lookouts," and their photos are kept in binders studied by the White House detail.

Officials added that they have kept tabs on some fringe groups that have expressed interest in attending some of the anti-Soviet rallies planned for next week. Among them are some split-offs from the militant Jewish Defense League, a New York-based group that has almost disintegrated recently because of the criminal prosecution of several members. JDL activists contacted said they plan to demonstrate next week, but will not cause any disruption.

Security officials said that while they believe the planned rallies will be peaceful, they fear that troublemakers can infiltrate even benign protests or somehow create diversions.

The summit will be a financial strain on the Secret Service, which officials say is stretched to the limit by such large-scale events, including its obligation to begin providing protection to all the major presidential candidates soon. "We will need the stamina and patience of Job as well as the understanding of all who assist us," agency director John R. Simpson said in a recent magazine article.

The agency will be forced to bring in numerous agents from its 60 field offices who spend the bulk of their time investigating counterfeiters and con artists.

D.C. police and Park Police also will be facing unknown costs from the summit, because they are placing officers on 12-hour shifts and will generate large overtime bills.

Fulwood sees these hundreds of officers -- who probably will end up standing for hours in the cold and never see any world leader -- as the heroes of the piece. He calls them "the grunts . . . . It's not so glamorous."

"When the day comes, we're going to make it work," Fulwood said. "It's a huge task."