Canadian sprinter Andre de Grasse finally delivered on his promise on Wednesday, powering to Olympic gold in the men's 200m final.

De Grasse, the 2016 Olympic 200m silver medallist behind Usain Bolt, raced home in 19.62sec to claim the first major championship gold medal of his career.

Kenny Bednarek of the United States took silver in 19.68sec while reigning world 200m champion Noah Lyles took bronze in 19.74sec.

American 17-year-old Erriyon Knighton finished just outside the medals in fourth in a time of 19.93sec.

De Grasse's gold medal completed a long journey back from injury and illness.

He exploded onto the international sprinting scene in Rio with a shock bronze medal in the 100m followed by his silver in the 200m behind Bolt.

But he failed to build on that Olympic debut after suffering hamstring problems and a bout of mononucleosis which sidelined him for much of the two years following his breakthrough in Rio.

However a change of coach helped him rediscover that form, and he signalled his return to the elite level at the 2019 World Championships when he won silver behind Lyles.

In Tokyo, De Grasse improved steadily through the rounds, posting the fastest time in Tuesday's semi-finals.

Starting in lane six in Wednesday's final, he made a smooth start and led coming into the straight to control the race, holding off the challenge of Bednarek and Lyles over the final 50 metres.