More than 100 activists met last night at the Old Cambridge Baptist Church to plan a Saturday demonstration against the recent escalation of U.S. involvement in Central America.

"The antiwar movement in this country during the Vietnam era was a party compared to what will happen if the Reagan administration holds out any longer," said Steve Norris, a member of Vecino, an organization that sends medical aid to Nicaragua.

The Central American Solidarity Alliance (CASA) planned the meeting Wednesday night on learning that about 3200 U.S. troops were sent to southern Honduras following reports that Nicaraguan forces had entered that country, according to Kevin P. Whalen, a CASA organizer enrolled in the Divinity School.

The activists voted unanimously to hold a demonstration Saturday at noon at Park Street, to hold a follow-up meeting this Sunday at the church.

"We've been working for seven years and we've found that this is probably the biggest escalation and the biggest threat to the sovereignty of Nicaragua that we've seen in seven years," Sweatland said.

Last night's meeting included members of numerous organizations concerned with Central America and "representatives of universities, trade unions, and everybody else," Sweatland said.

Several people at the meeting said they had attended a demonstration earlier yesterday in front of the Federal Building in Boston, during which protesters pushing on the glass of the building broke a window.