A man charged with impersonating a police officer and sexually assaulting a 12-year-old girl failed to show up yesterday for a trial on kidnapping and sex abuse charges, setting off a search by Montgomery County police and sheriff's deputies that could reach Cuba.

Authorities obtained a fugitive warrant late yesterday for Ricardo Perez-Ribalta, a lawyer and Gaithersburg businessman. Perez-Ribalta was charged with abducting the girl Oct. 16, 1989, and falsely identifying himself as a county police officer. Police said Perez-Ribalta called 911 from his mobile car phone to report a runaway, then drove the girl to a secluded area and assaulted her at knifepoint.

Perez-Ribalta, 37, was scheduled to be tried yesterday on charges of a first-degree sex offense, attempted kidnapping, a third-degree sex offense and impersonation of a police officer. Conviction of a first-degree sex offense can lead to a life sentence.

Circuit Court Judge DeLawrence Beard revoked the $100,000 bond for Perez-Ribalta after the defendant failed to show up for the start of the trial yesterday.

Perez-Ribalta's failure to appear in court angered county police, who said the defendant had been seen Saturday night at Lakeforest Mall in Gaithersburg buying clothes and driving a new car.

"There is no rhyme or reason for the setting of bonds," said Capt. Carol Mehrling, head of the police department's Youth Division, which investigates child sex abuse, neglect and physical abuse cases. "If he had been kept in jail as he should have been, we would not have to track him down."

Perez-Ribalta, a native of Cuba, has lived in Montgomery County since 1980, according to court documents. Before his arrest last year, he owned a janitorial company, General Maintenance Service Corp., in Gaithersburg.

Police said Perez-Ribalta allegedly stopped the 12-year-old girl and a 13-year-old girl as they were walking in Gaithersburg after running away from home. After the girls refused an offer for a ride, Perez-Ribalta identified himself as a police officer and pulled the younger girl into his car, police said.

Authorities traced Perez-Ribalta's 911 call to his cleaning service. Two former employees identified the voice on the police tape as Perez-Ribalta's, police said.

Police later confiscated a cellular telephone, police red light and handcuffs allegedly used by Perez-Ribalta. According to court documents, Perez-Ribalta admitted having sexual relations with the girl but denied using force.