Striking police rejected a city offer last night that would have ended a six-day-old walkout that has a stranglehold on the festive Mardi Gras season.

"Strike! Strike!," the officers shouted as they burst from a mass meeting called to determine whether they would settle with the city or carry on an increasingly bitter and widening fight.

Neil Curran, public relations officer for the Policemen's Association of Louisiana, said the offer had been rejected.

"There was no offer," he said. "It was a joke. It started with no amnesty."

Earlier, the policeman escalated the strike, throwing up picket lines at fire stations and garbage depots. Sanitation workers refused to cross the lines and no garbage was picked up, but firefighters stayed on the job.

Officials of the firefighters' union, whose contract with the city expires March 1, urged their men to continue performing duties. Fire department officials said they had no reports of firemen walking off the job.

The police strike already had prompted cancellation of all Mardi Gras parades in the city, and a group of merchants announced it was suing the police union for $30 million in damages because of carnival and Mardi Gras losses.

In another development, Civil District Judge Richard Garvey declared police union officials in contempt of court. He had declared the strike illigal Wednesday and left it up to the city to initiate contempt proceedings.

Garvey commanded union officers to appear at a hearing tomorrow. Maximum punishment would be six months in jail and a $500 fine.