One of two anit-Castro Cuban expatriates acquitted of murder and conspiracy in the 1976 car bombing assassination of former Chilean ambassador Orlando Letelier was sentenced yesterday to 4 1/2 years in prison for lying to the grand jury that investigated the case.

Guillermo Novo Sampol, who was serving a life term in prison until a federal appeals court granted him a new trial that resulted in his acquittal on the murder and conspiracy charges, will be eligible for parole almost immediately, and will have to serve no more than about nine months under the conditions of his sentence.

Novo, 41, was returned to jail yesterday, but his lawyer said he will ask the court to release him on bond pending an appeal of the perjury convictions.

In sentencing him, U.S. District Judge Barrington D. Parker rejected a plea from his lawyer that his client not serve any more time in jail since he already had spent nearly three years in prison on the more serious charges for which he has now been acquitted.

In 1979, a federal court jury here convicted Novo and codefendant Alvin Ross Diaz of murder and conspriacy in the Letelier case. But after the appeals court overturned their convictions, a second jury acquitted them May 30 on the murder and conspiracy charges. But the jury found Novo guilty of two counts of making false statements to the grand jury.

Letelier, 44, and an associate, Roni Karpen Moffitt, 25, were killed when a bomb exploded under Letelier's car as it rounded Sheridan Circle on Embassy Row on Sept. 21, 1976. It is still considered the most notorious act of international terrorism ever committed in Washington.

Calling Novo a "liar" and a "terrorist," Assistant U.S. Attorney E. Lawrence Barcella Jr. yesterday urged Parker to give Novo the maximum sentence -- 10 years in prison -- for his conviction on the two perjury counts. "I can't forget Ronni Moffitt and Orlando Letelier," Barcella said, adding that Novo's allegedly false statements to the grand jury a month after the assassination seriously hindered the government's attempt to solve the case.

Novo's lawyer, Paul A. Goldberger, said it would be "unjust" to send Novo back to prison. "It seems to me that [the government] wants you to sentence him for the murder of Orlando Letelier and Ronnie Moffitt, for which the jury found him not guilty," Goldberger said.

The government's chief witness at both trials, Michael Vernon Townley, an American-born agent for the Childan secret police, testified that under orders from his superiors he recruited the Cuban expatriates to help him carry out the murder of Letelier an outspoken critic of the military regime of Chile's military dictator, Augusto Pinochet.

Jurors at the second trial said doubts about Townley's truthfulness led to their not guilty verdicts on the murder and conspiracy charges.

Three jurors returned to the courtroom to watch Novo's sentencing. Juror Robin Whitten said she felt Townley was an assassin who got off easy with a maximum 10-year sentence. She told reporters that prosecutors failed to back up Townley's account with documentary evidence.

"There wasn't one clear thread that you could hold onto to find the police guilty," she said. "We went through everything."