Gunnaid Anding Taher Ford, 19, maintained his pleas of guilty in the Launceston Supreme Court today to assault and stealing.

The charges had been downgraded from armed robbery.

Crown prosecutor Luke Brett told the court that Ford, then 18, was with a group of people who entered Coles supermarket in Charles Street, Launceston, on September 26 last year.

Mr Brett said that CCTV captured Ford - twice - stealing from the confectionery aisle by placing chocolate bars down his pants.

A Coles employee confronted Ford about his stealing, but Ford went outside the store.

The employee used his mobile phone to call police.

When the employee said "Launceston police station", CCTV footage, which was played in court today, showed Ford taking several steps down the ramp to the entrance of Coles.

Ford is seen holding a black-handled knife above his head and making stabbing motions with it.

An associate pulls Ford away and he flees. 

Mr Brett said that Ford told his victim that he was going to kill him.

Defence counsel Evan Hughes told the court that the closest Ford came to his victim was five metres, so the chance of injury to the employee was minimal.

Justice Robert Pearce will sentence Ford on Thursday at 4pm.