Dustin Johnson surged to a five-stroke lead after the third round of the weather-plagued Genesis Open on a busy Sunday, boosting his hopes of jumping up to the the world No 1 spot.

The long-hitting Johnson stayed on course for his first top ranking with a sizzling round of seven-under 64 at the famed Riviera Country Club in Los Angeles.

His 17-under 196 total put him comfortably in front of fellow American Wesley Bryan, who shot 63 in the third round.

Johnson made a potentially tournament-winning move by finishing his round with three successive birdies.

The world number three quickly went back to work as officials tried to cram the tournament's final 36 holes into a long day of play.

Johnson will take top spot if he wins, as long as current number one Jason Day finishes lower than third.

That appeared assured as Australian Day had his worst round of the tournament, a 75, to stand 68th.

Bryan, a Tour rookie, had seven birdies, an eagle at number 10 with one bogey, at number eight, in going eight under for the round.

But he could not make up ground on Johnson. 

Padraig Harrington's 70 left him four-under for the tournament heading for his final round, with Graeme McDowell a shot further back after he carded a third-round 71.