A 28-year-old Indian man's appeal to throw out a nine-year jail sentence in a sexual assault case has been rejected by a US court.

The Supreme Court of Ohio last month declined to accept the appeal of Gurwinder Singh, upholding his February 2015 conviction by a Logan County Common Pleas jury for kidnapping and gross sexual imposition.

Singh, who was charged over a sexual assault in 2013 that occurred at the Valero gas station in Stokes Township where he worked at the time, is serving a nine-year sentence as a result of the 2015 conviction.

He was labelled a Tier II sex offender requiring him to register with authorities for 25 years.

An Indian national, Singh may also face deportation, the Bellefontaine Examiner reported.

He had entered a guilty plea to rape in late 2013 and was sentenced to five years in prison. The Third District Court of Appeals issued a ruling in 2014 allowing him to withdraw that plea after serving 10 months in prison.

He took the case to trial in February 2015 and was found guilty of both charges. Singh was then given a nine-year sentence.