A Montgomery County Circuit Court judge yesterday sentenced a Gaithersburg man to 30 years in prison for the strangulation of his pregnant girlfriend, whose decomposed body was left for 17 days in a car in a remote parking lot at National Airport.

Calling the murder "terrible" and "revolting," Judge Peter J. Messitte said he felt compelled to impose the stiffest possible sentence on Ahmad Nowrouzi, 28, an Iranian citizen who faces a deportation hearing next week.

"Some crimes are just so horrible that the community collectively has to respond and say we will condemn this as extensively as possible," Messitte said. "This is one of those crimes."

At yesterday's sentencing, Nowrouzi, a former restaurant owner, read a prepared statement to a courtroom filled with his relatives, as well as the victim's parents.

"There hasn't been a night that I have slept at peace," Nowrouzi said. "All of this is the byproduct of the fact that my dearest friend died in my very presence, and it became more tragic that I have been convicted of her death, a death that was never in my mode of thinking."

Messitte found Nowrouzi guilty of second-degree murder on July 17 after a six-day trial. Nowrouzi was convicted of strangling Marlene Forrester on July 1, 1989, in her Gaithersburg apartment after a dispute. In statements to police, Nowrouzi said Forrester, 26, died as result of choking on a seat belt while he was driving her to a hospital for treatment of a knife wound.

According to court testimony, Nowrouzi concealed Forrester's body in her 1986 Dodge Colt and drove the car to a far corner of the airport's Satellite B parking lot.

Forrester's body, covered by a rug, was found July 18, 1989, by a passerby who noticed an odor emanating from the car, police said.

Messitte said Nowrouzi's actions after the slaying were "as revolting as people will ever see." According to court testimony, Nowrouzi removed a bloody patch of carpet from the apartment, left several messages on the victim's answering machine and drove to South Carolina to visit his fiance'e. Witnesses said Nowrouzi was under pressure from his family to participate in an arranged marriage with the woman.

Nowrouzi twice returned to the airport to check whether Forrester's body had been found, police said. On one visit, a parking lot attendant jotted down the license tag number on Nowrouzi's Corvette.

Nowrouzi's attorney, Richard Lurye, asked Messitte to impose a 10- to 18-year prison term as recommended under the state sentencing guidelines. "Make this a chapter in his life, not the whole book," Lurye urged. "You have the power to turn this event into a transaction for hope rather than wreckage."

But prosecutor Kathleen Toolan said Forrester "was a person who did not deserve the fate she met. This was a hideous crime and coverup . . . that cannot go unpunished."

With the 30-year sentence, Nowrouzi is eligible for parole in about seven years.

He could face deportation when he is released. A hearing is scheduled Wednesday to seek Messitte's recommendation to the Immigration and Naturalization Service on whether Nowrouzi should be returned to his native country. Lurye said Nowrouzi could be executed if he is sent back because Nowrouzi's father had worked for the former shah of Iran.