PORT-AU-PRINCE, Haiti (AP) _ Four high-ranking army officers were discharged for drug trafficking a day after a visiting U.S. official tied resumption of U.S. aid to progress in stopping the drug trade, reports said Thursday.

Independent Radio Haiti Inter said the discharged officers are Lt. Col. Rosny Casimir, Lt. Col. Serge Toussaint, Lt. Col. Lionel Liautaud, and Lt. Col. Antoine Jean-Gilles Jr.

Casimir, Toussaint and Liautaud were staff officers at Army Headquarters, and Jean-Gilles was second-in-command at the Dessalines Barracks under the late Col. Jean-Claude Paul.

Paul, who mysteriously died in October after drinking pumpkin soup which officials said was poisoned, was indicted by a Miami grand jury in 1988 on three counts of drug running.

Radio Haiti Inter and privately-owned Tele Haiti, citiing unidentified sources of the Army High Command, said the four officers were discharged Wednesday night for their involvement in drug trafficking.

The state-owned Tele Nationale also reported the discharges Thursday night, saying it was ''for the good of the army.'' It gave no further details or reason for the discharges.

Tele-Haiti said an unspecified number of other unidentified officers were discharged but not not mention the reason.

Richard Melton, assistant undersecretary of state for Caribbean affairs, visited Haiti on Monday and Tuesday to consult Haitian President Lt. Gen. Prosper Avril on Haitian-American relations and the resumption of American aid, a U.S. Embassy communique said.

Melton said the resumption of aid depended on progress in establishing a civilian government, respect for human rights and stopping the narcotics trade.

Two-thirds of the $90 million annual U.S. aid package to Haiti was suspended after the violently aborted elections in November 1987 in which at least 34 voters were shot and hacked to death at the polls by thugs protected by soldiers.

Col. Gary Leon, former secretary of the Army High Command, was convicted this month in Brooklyn, N.Y., on charges of smuggling cocaine from Haiti, earlier this year. He is scheduled to be sentenced in May.