WASHINGTON — Senior Pentagon officials say Defense Secretary Richard Cheney and his NATO counterparts are to discuss additional European nuclear cuts in a NATO nuclear planning group meeting in Sicily Oct. 17 and 18.Also, at the 50th meeting of the nuclear planners since the North Atlantic Treaty Organization was formed, the defense ministers are to discuss revising the command structure of military units assigned to NATO in the aftermath of the cold war and in light of shrinking forces. Senior Pentagon aides, who asked not to be identified, say additional nuclear cuts will be considered. President Bush announced last month that the United States will remove short-range nuclear missiles and nuclear artillery shells from Europe but he said that nuclear bombs for delivery by aircraft would remain. Partly as a result of this announcement, one official says, NATO ministers will examine "how NATO's nuclear forces can be shaped, molded, and adapted to reflect the changed security climate that the alliance now faces and to fulfill the mandate of the 1990 NATO summit in London to seek the lowest and most stable level of nuclear weapons needed to secure the prevention of war." But, the official added, "We are committed to maintaining a nuclear element in NATO's deterrent and ... committed to maintaining that element modern and up to date where necessary." Aides to Mr. Cheney say that with the size of the US contingent in Europe shrinking and European militaries declining, the officials also will talk about the command structure needed to operate the remaining troops.