SINGAPORE - A 71-year-old business development manager, who was in an MRT train after a drinking session, walked up to an American man and asked if he wanted to have sex with him.

Gan Thean Soo turned violent when Mr Joseph Flynn De Marini, 25, said that he was not gay. Gan then hurled vulgarities at the younger man and slapped him on the left side of his face.

The American recorded the incident on video and uploaded it onto Facebook. It went viral.

Gan pleaded guilty on Friday (April 20) to one count each of harassment and assault.

One charge of being a public nuisance will be taken into consideration during sentencing.

The court heard that Mr De Marini boarded the train with a Singaporean friend, Ms Li Zixin, 20, at Chinatown station at around 8.15pm on April 19 last year and they sat opposite Gan in the same carriage.

Mr De Marini ignored Gan when he noticed that he was staring at him as the train was passing by Farrer Park station.

The elderly man then walked towards the American and told him: ""I like you. I am gay."

Gan also propositioned the young American.

He got angry when Mr De Marini and Ms Li chided him for being rude and started hurling vulgarities at the American.

Deputy Public Prosecutor Charleston Teo said: "The victim throughout this exchange informed the accused that he did not know who he is and repeatedly requested for the accused to leave them alone.

"The victim then informed the accused that he was not gay. The latter however, continued insisting otherwise."

In the video that is about four minutes long, the other passengers could be heard intervening but Gan continued harassing Mr De Marini. One passenger took Gan aside and he admitted that he "drank a lot" earlier that evening.

Gan then approached Mr De Marini again and said: "Can I kiss you? I want to kiss you."

He continued insisting that the American was gay before slapping the left side of the latter's face.

Mr De Marini did not retaliate, the court heard. Another fellow passenger then came forward and took Gan away from him.

DPP Teo told District Judge May Mesenas: "The accused continued insisting that the victim had 'signalled' him and that he was jealous that the victim was touching a woman."

Gan, Mr De Marini and Ms Li later alighted at Serangoon station but via different doors.

The American alerted the police about his ordeal two days later.

Gan is now out on bail of $8,000 and he will be back in court on April 27.

For committing assault, he can be jailed for up to two years and fined up to $5,000.