Three men accused of obtaining classified Pentagon documents for GTE Corp. have asked a federal judge to throw out the case against them, charging that the Justice Department bowed to pressure from Sen. Charles E. Grassley (R-Iowa) in seeking the indictments.

In motions filed late Monday in Alexandria, the three current and former GTE employes contend that the Justice Department is selectively prosecuting them because of "arbitrary political considerations" and "pressure coming from Sen. Grassley."

Their attorneys attached a letter that Grassley wrote to Attorney General Edwin Meese III about the GTE case before the indictments, as well as the prepared testimony of former Pentagon official Robert L. Segal, who appeared before Grassley's Senate Judiciary subcommittee last week.

The motions before U.S. District Court Judge James C. Cacheris have provided ammunition to Grassley's critics within and outside the Justice Department, who contend that the senator may have jeopardized a pending criminal case. Grassley has maintained that his criticism does not affect the case and that the Justice Department is trying to divert attention from its poor record in defense procurement cases.

But a federal law enforcement official complained that "senators are putting pressure on the Justice Department to prosecute without regard to the state of the evidence or whether the case is proper or improper. We're going to start seeing allegations of prosecutorial misconduct . . . in every one of these cases that a senator decides to get into.

"It destroys the credibility of the prosecutorial function. The American people don't want cases prosecuted because a U.S. senator says so."

A GTE subsidiary pleaded guilty last month to improperly obtaining classified Pentagon budget documents related to electronic warfare contracts and agreed to pay $590,000 in fines and penalties.

The three men indicted in the case have pleaded not guilty. They are Bernie Zettl of McLean, a retired Air Force major and former consultant to GTE and other defense contractors; Walter R. Edgington of Annandale, a GTE vice president, and Robert R. Carter of Mountain View, Calif., former marketing director of the company's electronic warfare unit.

Their attorneys charged in court that Grassley "specifically urged Attorney General Edwin Meese to obtain an indictment in the investigation of GTE . . . ."

In an April 9 letter to Meese, Grassley said he was "very disturbed" by a Wall Street Journal account of the GTE probe. "While not commenting on any specific case, I would urge that generally, as a policy matter, the Department of Justice take action to prosecute those involved in any such trafficking conspiracies," he wrote.

Arguing that their clients have been singled out for what is a common industry practice, the defense lawyers cited Segal's statement that at least 25 other companies are under investigation for obtaining internal Pentagon documents. Grassley agreed to halt Segal's testimony after a Justice Department official vehemently objected.

Grassley had hoped to resume Segal's testimony yesterday. But Judiciary Committee Chairman Strom Thurmond (R-S.C.) barred Grassley from holding the hearing for at least a month because of Thurmond's concern that it could interfere with the pending case.