Harvard may block a recently announced Cambridge proposal to solicit Federal urban renewal funds for Harvard Square if the University cannot reach an agreement with the City on the long-term use of Harvard land in the Square.

Charles P. Whitlock, assistant to the President for civic and government relations, said yesterday agreement on construction of a "Holyoke-type" building on the University-owned Chruch Street garage site, and a pedestrian mall linking Church St. with Appian Way and Radcliffe Yard would be major considerations in the decision.

The University could block Cambridge urban renewal plans by not allowing the City to use the approximately $10 million Harvard has spent improving its own land as an urban renewal tax credit.

Under the federal Urban Renewal Act, cities are allowed to consider university-spent land-improvement money as part of the 17 per cent city share of the Federal-State-City expense sharing plan. The federal government puts up 66 per cent of urban renewal costs, and the state the final 17 per cent.

Paul J. Frank, executive director of the Cambridge Advisory Committee, conceded yesterday that the $10 million tax credit was essential to any urban renewal in Harvard Square, and "no action can be taken without it."

Cambridge officials are talking to the University about the money, but it is too early to make any definite statement on progress of the talks, Frank said.

Some local officials consider urban renewal a way to stop the University's expansion in Cambridge, Whitlock said.

The University fears being "locked into" a 20-year development plan for Harvard Square, Whitlock explained. Federal urban renewal plans must be protected over at least a 20 year period.

Harvard does not want to be forced into the position of having to ask the Cambridge Redevelopment Authority for permission to change the use of the land if the need arises, Whitlock said.

The University backed out of two projects in 1961 and 1963 because of failure to reach a similar agreement on future land use.

Alan McClennen, city planning director for Cambridge, indicated yesterday that the Planning Board would ask the Cambridge City Council August 14 to authorize funds to begin studies of possible Urban Renewal projects in the Harvard Square area. The price tag for the studies could be as much as $500,000 McClennen said.

"Everybody says that something needs to be done to Harvard Square," McClennen added, "and I can't help feeling that Urban Renewal is the logical path."