Six ships led by the USS Mississippi, a guided missile cruiser, will join the aircraft carrier USS Coral Sea and its escorts operating off the Caribbean coast of Central America, the Pentagon announced yesterday.

The maneuvers will bring to 17 the number of U.S. ships operating near Nicaragua in a show of force that U.S. officials have said is intended to intimidate the Sandinista regime there.

The Coral Sea is exercising with four other ships in the western Caribbean, and the battleship USS New Jersey and five other ships are due to arrive off the Pacific coast of Central America Friday.

The Mississippi will be in the Caribbean to take part in the semiannual NATO readiness exercise in the western Atlantic and eastern Caribbean. Readex 2-83, as the maneuvers will be called, will involve 32 ships and 35,000 military personnel from today until Sept. 17.

With the exception of the Mississippi's joining the Coral Sea for an undisclosed number of days, the Readex maneuvers will be separate from the politically controversial current exercises in Central America, Pentagon officials said.

The maneuvers will involve one Dutch and two British ships, two U.S. attack submarines and two aircraft carriers, the USS Independence and USS John F. Kennedy.

Navy officials said it is unusual but not unprecedented for three aircraft carriers to be operating in the Caribbean at the same time. They also said a Readex exercise of similar size was conducted last March, and similar maneuvers have been staged at least once a year since 1954.

The Pentagon declined to say when the Mississippi and its group would break away from Readex or how much time the ships would spend with the Coral Sea.