The Senate Rules Committee kicked off the congressional observance of Franklin D. Roosevelt's centennial yesterday by approving plans for a long-delayed memorial in Washington to the 32nd president.

This is the first time any committee of Congress has voted in favor of authorizing the memorial since the site for it -- West Potomac Park -- was approved in 1959.

The committee voted 7-0 (five Republicans and two Democrats) to authorize spending "such sums as may be necessary" to build a memorial on a site near the Tidal Basin, in the same general area as the Washington Monument and the Lincoln and Jefferson memorials.

Franklin D. Roosevelt Jr., the former president's youngest son, said yesterday he had never been particularly supportive of a memorial because he feared it would cost too much to build and maintain and might be architecturally wrong. But, he said, he did not object to the most recent design by Lawrence Halprin.

Both houses of Congress would have to approve the authorization, as well as a bill appropriating the money, before the memorial could be built.

A commission to oversee creation of a memorial to Roosevelt was created by Congress in 1946, one year after his death, but the memorial has been delayed by disputes over its design and cost.

Sen. Mark O. Hatfield (R-Ore.), chief sponsor of the resolution authorizing the memorial, said a previous design was rejected by the Roosevelt family. He said a previous authorization measure failed to win committee approval because of objections to its cost.

The cost of the memorial was estimated in 1979 at $23.25 million.

The latest design, by architect Lawrence Halprin, calls for a memorial dominated by a 14-foot-high granite wall, through which visitors would enter a series of gardens high-lighted by waterfalls.

Hatfield said the design has the approval of the family as well as of the federal Fine Arts Commission.

He said the role of water in the memorial was fitting because of FDR's World War I service as assistant secretary of the Navy and the importance of water to the therapy he received for polio.

Roosevelt would be 100 years old on Saturday if he were alive. Congress plans a joint session on Thursday in observance of the centennial.