A mistrial was declared tonight in the arms smuggling trial of Kazem Zamani of Gaithersburg when the jury reported it was deadlocked after five days of deliberations.

Zamani, 42, was charged in U.S. District Court here with conspiring to smuggle millions of dollars worth of U.S. military equipment to his native Iran in violation of the U.S. Arms Export Control Act.

Zamani, an import-export entrepreneur and real estate manager, appeared relieved when federal Magistrate Frederic N. Smalkin granted the defense's request for a mistrial.

Smalkin sat in yesterday while U.S. District Judge Frank A. Kaufman, who had been hearing the case, attended a judicial conference.

One of the jurors, who asked not to be identified, said members of the jury were split, with 10 of them favoring a conviction and two members holding out for acquittal.

Prosecutor Arthur F. Fergenson would not comment tonight on whether the government will seek to retry the case.

Zamani remains in federal custody.

Zamani's arrest in June was one of a series of federal actions from Alexandria to San Diego involving Iranian nationals, and in at least two cases, United States military men.

Zamani was caught in a four-year U.S. Customs Service undercover project called "Operation Exodus," which is aimed at stopping the covert flow of American technology to the Soviet Union and other Eastern Bloc nations.

The federal crackdown recently netted arms and parts for weapons destined for Iran and Libya, according to Customs spokesman Ed Kittredge.

"The Iranians presently are busily trying to replace arms provided by the U.S. to the shah [that] they have spent in their lengthy war with Iraq," Kittredge said. "We're just discovering it -- we've had these two big cases involving military men -- that's a new wrinkle." He was refering to the arrest July 31 of Lt. Col. Wayne G. Gillespie of Alexandria on charges of bribery and of the arrest earlier this summer in San Diego of seven persons, including a Navy seaman, as part of an alleged conspiracy to steal spare parts for F14 fighter planes for sale to Iran.

By last March, Operation Exodus agents had secured 369 convictions, according to Kittredge. More than two dozen other cases are pending nationwide, he said. The federal agents have seized nearly $300 million worth of equipment during the four-year program, Kittredge added.

During Zamani's 11-day trial, his attorney, Domenic R. Iamele, told the jury of nine women and three men that federal agents, working undercover, entrapped his client, playing on the 42-year-old Iranian's "money lust."

But federal prosecutors Fergenson and Susan M. Ringler argued that Zamani had conceived the idea, approaching a Gaithersburg exporter in April 1984 and later an undercover agent posing as a supplier, about obtaining five Varian 145E military radar tubes from a U.S. supplier for delivery to unknown buyers in London for ultimate shipment to Iran.

The jury after less than four hours of deliberations last week, asked Kaufman to allow them to listen again to more than seven hours of wiretap tapes made by federal agents discussing with Zamani the procurement of $15 million worth of special radar components as well as a six-page list of parts for worn U.S. jet fighters, helicopters and tanks in Iran.

Had he been convicted, Zamani, who has retained his Iranian citizenship while using a permanent resident visa since he came to the United States in 1979, would have faced deportation after serving any sentence he received.