Alexander Rossi capped off a dominant weekend by taking his third IndyCar victory in Sunday's Grand Prix of Long Beach, leading all but 14 laps en route to a comprehensive win for Andretti Autosport.

Ex-Manor Formula 1 driver and 2016 Indianapolis 500 winner Rossi led three out of four practice sessions before taking pole position on Saturday, and carried his good form through to Sunday's 85-lap race.

Rossi enjoyed a decent pace advantage over the field throughout, only losing the lead through the pit stop cycles, but was never comfortable up front as four caution periods bunched the field together.

Rossi came under the greatest amount of pressure in the closing stages as Penske driver Will Power used his push-to-pass boost which he had conserved through the race, but the Australian was unable to find a way past.

The result in his home state of California marked Rossi's third IndyCar win following his Indy 500 success in 2016 and last year's victory at Watkins Glen, and catapulted him into the lead of the drivers' championship after three rounds.

"I can't really put into words how good the car was all weekend," Rossi said. "I think we proved that and I'm just so glad we were able to capitalize and nothing crazy happened. This one I'll definitely remember for a very long time for a lot of different reasons."

Power was left to settle for second, finishing 1.2 seconds behind, while Chip Ganassi Racing's Ed Jones benefitted from a late caution to rise to third place, marking his first podium finish since last year's Indy 500.

Andretti rookie Zach Veach took an impressive fourth place ahead of Graham Rahal, who recovered to fifth after receiving a drive-through penalty for punting Simon Pagenaud off the track on the opening lap of the race.

Marco Andretti finished sixth ahead of defending series champion Josef Newgarden, with Tony Kanaan taking eighth for AJ Foyt Racing. James Hinchcliffe took ninth for Schmidt Peterson Motorsports, while Charlie Kimball rounded out the top 10 for Carlin.