AN 18-year-old American student who spray-painted graffiti on cars with a group of friends was sentenced to four months' imprisonment and six strokes of the cane in a Singapore court yesterday. The sentence prompted a strongly critical response and a hint of retaliation from the American Embassy. Michael Fay had pleaded guilty to five charges of vandalism, mischief and dishonestly keeping stolen property. Apart from the jail and caning penalties, he was fined a total of S$3,500 (HK$17,062). Fay was released on bail and planned an appeal. He is believed to be the first foreign Caucasian to be sentenced to caning. Offenders sentenced to caning are strapped to a trestle and beaten on their bared buttocks with a length of rattan. The caning can break the skin. A Hong Kong youth, Shiu Chi-ho, 16, will face similar charges when his case is heard on Tuesday. His lawyers had said he would not plead guilty. When District Judge F. G. Remedios announced Fay's sentence, his mother sobbed uncontrollably and fellow students from the American school looked shocked but the accused was expressionless. Outside the courtroom, Ralph Boyce, charge d'affaires of the American Embassy, said that the United States Government recognised that Americans overseas were subject to the laws of host countries in which they were guests. ''However, we see a large discrepancy between the offence and the punishment,'' he said. ''The cars were not permanently damaged. The paint was removed with thinner. Caning leaves permanent scars.'' He said the embassy had made its concern clear to the Singapore Government regarding ''this type of punishment'', particularly for a youthful, first-time offender. In mitigation, Fay's defence counsel R. Palakrishnan, had tendered two psychiatric reports which stated that Fay was suffering from residual symptoms of a form of neurological disorder. His parents had divorced when he was nine and he had showed signs of emotional disturbance in his early teens. Deputy Public Prosecutor Ng Cheng Thiam tendered a report by a government consultant psychiatrist who said that Fay might have suffered from some form of neurological disorder as a child although he was not convinced of it. Judge Remedios said he accepted the government psychiatrist's finding that Fay's actions were ''not acts that were beyond his ability to resist or control''. He said the fact that 18 cars had been deliberately and wilfully vandalised within 10 days was very serious. Earlier, a 15-year-old Malaysian youth pleaded guilty to similar charges in Juvenile Court. He was placed on pre-sentencing probation until April 5, when his case will be reviewed. When the arrests of the youths were first announced, media reports said members of the public were demanding tough action against the youths. In a letter to The Straits Times, a reader congratulated the police on their resolve to bring foreign student vandals to court and said they should be ''caned and jailed, then deported''. One of those arrested, a 17-year-old Australian youth jumped bail and left the country with his parents.