A Drug Enforcement Administration informant, testifying in a major drug trial in U.S. Court in Alexandria, said yesterday one of the defendants last year tried to arrange to buy hashish from an unnamed embassy in Washington.

Federal prosecutors did not ask the witness, John Snow of Naperville, Ill., which embassy was involved, but sources familiar with the case said Snow had named a South American embassy in earlier grand jury testimony.

Snow said yesterday he had once worked for the defendants, who are accused of operating a major international drug ring over several years. But Snow said he later told DEA agents about his involvement in the drug business.

Snow, who became a paid DEA informant, testified that last fall defendant Michael Vlcek told him to buy a pickup truck in Chicago, "go to Washington, meet someone at the embassy. We were supposed to pick up suitcases, and the suitcases were supposed to have hashish in them."

Assistant U.S. Attorney Justin W. Williams, a prosecutor in the case, said last night he did not know the identity of the embassy Snow referred to and said he could not comment on the case.

Snow said he bought the truck on Oct. 13 and later Vlcek told him he was going to Washington "a week early to check things out" with the embassy. Vlcek called later and said the deal had fallen through, Snow said.

Under defense questioning, Snow said that he had once received psychiatric help after being court-martialed in the Army. Defense attorneys also stressed that Snow had been paid $3,100 as a DEA informant.

On Wednesday, another prosecution witness recanted parts of testimony he had given earlier to a federal grand jury investigating the alleged drug ring. That witness, James Monroe Justice, said he had been pressured by prosecutors to say anything to the grand jury and that he "kind of hedged on things."