A federal judge in Alexandria yesterday sentenced former State Department official Walter Reed Martindale III to 10 years in prison for conspiring to transport firearms in a plot to kill a Saudi sheik.

U.S. District Court Judge Albert V. Bryan Jr. sentenced Martindale, a resident of Fairfax County, on seven different counts, including impersonating a U.S. diplomat and transporting an Uzi semiautomatic rifle.

The judge dismissed as "ludicrous" Martindale's explanation that he had purchased the Uzi as part of a legitimate business proposal involving the security of rich Arabs.

He sentenced Martindale to a total of 21 years in prison on the seven charges, with 11 years to run concurrently.

"I didn't believe it the explanation and obviously the jury didn't believe it. It's a very bizarre statement," the judge said before sentencing Martindale.

Defense attorney Paul R. Kramer had asked that Martindale be sentenced to community service work among the Vietnamese in Northern Virginia, noting that the defendant had won medals evacuating Vietnamese after the fall of Saigon.

But Assistant U.S. Attorney Justin Williams, who acknowledged Martindale's "exemplary background" as a Navy officer and a State Department official, insisted, "The evidence still shows he was involved in a contract killing . . . a cold, ruthless act."

Martindale, 41, wearing a blue pin-striped suit and burgundy tie, sat expressionless in the courtroom yesterday, as he had throughout last month's week-long trial.

His only words to the judge were, "I am willing to accept any sentence you wish to give me." He was released on $25,000 bond pending appeal.

Prosecutors say it is unclear which member of the Shamsuddin Fassi family was the target of the abortive assassination plot.

The Fassi family was living in England four years ago when Martindale was arrested for transporting an Uzi semiautomatic rifle and a .38-caliber revolver from National Airport into London's Gatwick Airport.

After Martindale pleaded guilty in a London court to possessing the weapons, the U.S. government began the investigation that led to this arrest and trial in Alexandria.

Martindale testified last month that he had purchased the Uzi at the request of Ibrahim Rawaf, his partner in the Washington-based American International Trade Group, and that the weapon was to be used for security purposes.

According to the prosecution, Martindale was to receive $50,000 for his financially troubled company from unidentified Arabs for transporting the gun in the plot to assassinate a member of the Fassi family. Rawaf, who was also charged in the conspiracy, is a fugitive in Lebanon.

Defense attorney Kramer, who said he had already drafted Martindale's appeal papers, said the trial was marred by "incorrect recollections of Scotland Yard officials" and a "troubling lack of evidence."