Prime Minister Tadeusz Mazowiecki, campaigning for the presidency, urged the Soviet Union to withdraw its forces from Poland by the end of next year.

Good relations will be served by the withdrawal of Soviet forces from Poland by the end of 1991 and the abandonment of agreements such as the Warsaw Pact, "to be replaced by bilateral agreements of sovereign countries," Mazowiecki said Sunday in a nationally televised address.Some 55,000 Soviet troops are stationed in Poland.

Mazowiecki and Solidarity founder Lech Walesa are the prime contenders in early elections that were called for Nov. 25 after Gen. Wojciech Jaruzelski, a former communist, agreed to yield his presidential post more than one year into a six-year term.In other news . . . MICHAEL MILKEN, Drexel Burnham Lambert Inc.'s former junk bond chief, is expected to be sentenced next week for six securities felonies, the judge hearing the matter said Monday. . . . A SMALL AMOUNT of cocaine was found in a hangar at the Kennedy Space Center where space shuttles are readied for launch, NASA officials said.