PHILADELPHIA -- As demonstrators streamed into the Republican convention host city on Thursday, city police unveiled a security plan that relies on close supervision to keep rank-and-file officers from snapping during rowdy protests.

In hopes of avoiding the violence that overshadowed recent protests in other U.S. cities, Philadelphia police said they would more than double the usual number of supervisors on duty by organizing police into smaller teams of five or six officers.

Tear gas would not be used except under the most extreme circumstances, while immediate police action would be taken only during emergencies such as vandalism or assaults on officers.

Police Commissioner John Timoney said nonviolent protesters using civil disobedience in the manner of Martin Luther King would be approached in a calm manner, only after orders had been issued by senior officials.

"Great thought will be given to the tactics deployed," Timoney told a news conference outside police headquarters.

"We have eliminated, as much as is humanly possible, situations where officers will act as individuals. We are training our police officers and demanding that they act as a team, and then only under the direction of a supervisor."

Protest organizers, who have long complained about police surveillance, welcomed the message of restraint but said they remained skeptical given the nationally televised violent arrest of wounded car-jacking suspect Thomas Jones only two weeks ago.

"(The police) understand there is going to be civil disobedience. They understand that this is going to be a difficult week," said Stefan Presser, legal director with the American Civil Liberties Union of Pennsylvania.

"But they also seem to understand that in a democracy, we have to tolerate some disruption of the political process."

The Republican National Convention, which will nominate Texas Gov. George W. Bush for president, runs July 31 to Aug. 3 in the city where the Founding Fathers adopted the liberties enshrined in the Declaration of Independence and the U.S. Constitution.

Thousands of protesters representing causes ranging from social justice and the environment to organized labor and women's rights also will be in town to try to disrupt the proceedings by blockading streets and hotels with nonviolent direct action protests such as sit-ins.

Civic leaders, who view the convention as a rare chance to showcase Philadelphia's recovery after decades of decline, fear protests could lead to image-damaging violence of the kind seen at the World Trade Organization last year in Seattle.

"We're looking to make things as normal as possible," said Timoney, noting that street closings have been kept to a minimum. "People should come in and enjoy (the city). There's going to be a lot of good fun."

Timoney or one of his two top lieutenants will be on duty throughout the convention, beginning Friday afternoon.

City police are part of a larger convention security net that includes the U.S. Secret Service, the FBI and state police officers from Pennsylvania, New Jersey and Delaware.

The Philadelphia department has cancelled leaves and extended shifts to 12 hours to boost its effective available manpower from 6,800 officers to nearly 10,000, Timoney said.

Policemen also have undergone months of training to withstand what senior officials expect to be a barrage of verbal abuse from agitators intent on provoking violence.

"They must take verbal taunts, verbal abuse, disparaging remarks regarding their race, their ethnicity, their family origins," Timoney said. "Any verbal barrage that comes their way, they must take."