In a move to bolster U.S. military power near Cuba and the rest of the Caribbean, the Navy yesterday announced its intention to reopen portions of the former naval station in Key West, Fla., so that destroyers and other warships can once again operate from there.

Navy Secretary John F. Lehman Jr. said a "forward operating base" at Key West would support naval operations and exercises in the Florida Straits between the United States and Cuba and also "improve the Navy's response time to possible contingencies in the Caribbean area."

Reactivation of the naval station fits into an administration strategy that places more attention on pressuring left-wing governments in Central America and having more U.S. forces in a position to move quickly in an emergency against any Cuban or Soviet naval threat.

In his annual report to Congress this year, Defense Secretary Caspar W. Weinberger called attention to the threat that the Cuban Navy could pose in a wartime emergency to the 45 percent of U.S. shipping and oil-delivery vessels that move through the Caribbean or in and out of U.S. ports on the Gulf of Mexico en route to Europe.

Key West, at the southern tip of Florida and 90 miles from Cuba, was once a bustling naval air, surface and submarine base, but use of the complex has dropped off sharply in recent years. Lehman announced yesterday, however, that the Navy had decided to move ahead with a $20 million renovation plan and to reclaim a portion of the base's Truman annex that the Navy had previously declared as excess.

Lehman said Key West would be the home port for a squadron--normally six ships--of the Navy's new PHM missile patrol boats. This had been planned.

But Lehman also said that the harbor at the Truman annex "will be restored to permit frequent and regular visits by destroyers and other units of the Atlantic fleet," that other ships and aircraft squadrons would be operating out of Key West on a temporary basis more frequently, and that the base could also become a future home port for warships other than the missile boats.

In February, The Washington Post reported on plans to reopen Key West and the possibility that it might also become home to a squadron of six destroyers. At that time, it was also reported that part of the rebuilding plans included using Key West as an intelligence-gathering and analysis center for an expanding U.S. effort to keep tabs on Soviet and Cuban activity.

Although Lehman did not mention this in his public statement yesterday, sources said that it was still part of the plan.

The Navy said that it could accomplish its plans at Key West by reclaiming only about one-third of the 133 acres that had been declared excess in the early 1970s. The rest will be available for sale.