"I've decided to continue again for next year but I doubt I'll go for 2000. I think new century, new job," the Australian said yesterday.
Doohan, 33, who has won 52 grands prix, said his love of the sport was what kept him going.
"I still really enjoy riding the motorcycle and when that starts to slacken, that's when I'll give it away," the Honda rider said.
Doohan leads the championship standings this year by 21 points from Italy's Max Biaggi and the cancellation on Monday of next month's Brazilian Grand Prix means he could retain his title at this weekend's round at Phillip Island in Australia.
The international federation, the FIM, said the Brazilian race had been cancelled because Rio de Janeiro's Nelson Piquet circuit, which had been due to host the 14th round of the championship on 18 October, failed to pass a safety inspection. The race would not be replaced or rescheduled.
The decision leaves just two rounds remaining in the world championship - at Phillip Island on 4 October and Buenos Aires, Argentina, on October 25.
"With Brazil now out it's mathematically possible for me to win the title at Phillip Island, but that won't change the way I approach this race," Doohan said. "I go into every race trying to win and if I can do that at Phillip Island the championship will take care of itself."
Victory would give Doohan at least a 26-point advantage going into the final race. A grand prix win is worth 25 points while the second-placed rider scores 20.
Doohan leads with 210 points, 21 clear of Biaggi, who is second on 189 ahead of the Spaniard Alex Criville on 182.
"There's still two races left and 50 points up for grabs so no one has won anything yet and Biaggi and Criville are still in the equation," said Doohan.
"I'll keep my head down at Phillip Island. If the championship comes this weekend that's good, but nothing is certain until it's over."
The opening practice and qualifying sessions at Phillip Island will be held on Friday.Reuse content