With the Republican National Convention just days away, a judge ruled Wednesday that antiwar organizers could not hold a massive rally in Central Park on Sunday.

The decision marked the second time in a week that a state or federal court judge refused to overrule city officials and allow antiwar groups to rally in the city's most prominent park.

"The right to free speech does not guarantee plaintiff the best channels or location for its expression," state Supreme Court Judge Jacqueline W. Silbermann wrote in an opinion released Wednesday.

Silbermann admonished the antiwar group, United for Peace and Justice, for waiting more than three months after city officials denied it a permit to go to court. City officials, she wrote, had offered a suitable alternative: the West Side Highway, along the Hudson River.

The demonstration itself will go on, with as many as 250,000 protesters expected to march past Madison Square Garden, site of the convention, which begins Monday. But it is unclear where they will rally after passing the site.

Chris Dunn, a lawyer with the New York Civil Liberties Union who argued the case for the activists, expressed frustration with the ruling. The judge, he said, "may be the only New Yorker who can't tell the difference between the West Side Highway and Central Park."

City officials have consistently argued that Central Park's Great Lawn could not hold the estimated number of protesters and that so many feet would damage the refurbished turf. Of late, Mayor Michael R. Bloomberg (R) has argued that the park poses a security challenge. (Privately, however, senior police officials have said it is less difficult to police a demonstration in a park than along city streets.)

Police Commissioner Ray Kelly issued a written statement after the ruling, noting that his department would work to find an alternative location for the rally. Police and organizers are expected to meet and reach an agreement by Thursday.

Outside the courthouse in Lower Manhattan and just steps from an oversized megaphone representing free speech, Leslie Cagan, national coordinator for the group, vowed that "this decision will not be used to silence us."

Cagan added that the group remained against holding a rally along the West Side Highway, arguing that the exposed location poses health risks during summer and is far removed from the city's symbolic center.

A number of potential protesters have spoken of going to the park on their own Sunday. Cagan did not discourage this. "This decision," Cagan said, "does not speak to whether individuals or groups of people can go to Central Park."

She added that organizers will not lead protesters to the park. The point of the march and rally, she said, is to find peaceful resolutions to conflicts, and she said she remains committed to applying that philosophy to the negotiations.