ALEXANDRIA, Va. (AP) _ Army Col. Juan Lopez de la Cruz was cleared by a jury of conspiracy and bribery charges Thursday in a case in which in which he was accused of helping an Illinois arms contractor secure $3.7 million in weapons sales to El Salvador.

Jurors said they simply didn't believe the contractor, who was the government's chief witness in its attempt to prove two counts of conspiracy and one of bribery.

Lopez was accused of accepting $70,000 and a Rolex watch from Dennis Reese, president of Springfield Armory in Genesco, Ill.

According to the government's case rejected by the jury through its verdicts of innocent, Lopez told Reese Springfield Armory could receive tax- free money by telling the Defense Security Assistance Agency that commissions had been paid to an agent.

A Salvadoran resident would then act as the fake agent, cash the commission checks and return the cash, minus a fee, to Reese.

Reese was the prosecution's star witness in U.S. District Court in the Washington suburb of Alexandria.

''The testimony of the witness was not credible enough ... just no proof,'' said juror Bonnie Basara, 22, of Chantilly, Va.

Another juror, who declined to give her name, said, ''The prosecution's case was weak.''

Defense lawyers throughout the case attempted to discredit Reese, who testified under a grant of immunity from prosecution.

''Dennis Reese has committed more crimes than he has fingers on his hands and toes on his feet,'' declared defense attorney Barry Levin.

Upon hearing the verdict, Lopez, 49, said he felt as if 500 pounds had been lifted from his shoulders.

''I feel wonderful. I was hoping my name would be cleared,'' he said.

Lopez, a Cuban native who joined the Army after participating in the Bay of Pigs invasion in 1961, is commander of the Military Ocean Terminal Bay Area in Oakland, Calif.