Construction in Harvard Square will begin within two months on the first phase of the state's plan to extend Red Line subway service to Arlington, a city planning officer told a meeting of the Cambridge Transportation Forum last night.

John R. Hixson, an employee in the city transportation office, said workers will begin building a temporary station to handle Harvard Square passengers while the subway line is being extended, "by about late October or November." The temporary station will occupy a site on the Eliot St. MBTA yards, near where workers are now building the new John F. Kennedy School of Government.

Hixson added that the entire project, which will add five stops to the Red Line at a cost of about $600 million, will be completed in about five or six years.

The federal government is paying 80 per cent of the cost of the project. Engineers say the construction will alter the appearance of the Square by adding more sidewalk area and re-routing some of the streets in the area.

The proposed construction has drawn fire from many residents of Arlington, who argued that the new subway stops would attract commercial developers who would in turn disrupt neighboring areas with large shopping and hotel complexes.

The views of several Arlington residents who had contacted members of the forum over the summer, were also discussed at the meeting, but the members did not take a stand for or against the construction.

Dean Johnson, chairman of the forum, which is a five-year-old citizen's advisory group, said at the meeting that workers who have begun construction north of Cambridge are doing "a very competent and professional job."

Construction plans call for the workers to use the "cut and cover" method of excavation, which city planners maintain will reduce disruption of traffic near the construction site by insuring that excavated areas are covered over shortly after digging begins.