Los Angeles - Five-time major champion Phil Mickelson fired six birdies in a six-under par 66 on Saturday to maintain his two-shot lead in the PGA Tour Desert Classic.

The 48-year-old American heads into Sunday's final round chasing a 44th PGA Tour title and his third in this event in the California desert east of Los Angeles.

His 22-under par total of 194 put him two strokes clear of Canadian Adam Hadwin, who fired a bogey-free seven-under par 65 for 196.

Mickelson - who launched his week with a sparkling 60 on the La Quinta course, one of three in use this week - kept his foot on the accelerator on the tougher Stadium course on Saturday, where a chip-in at the sixth hole launched a string of three straight birdies.

"Every now and then you just need that putt, chip, something to fall and give you a little momentum," Mickelson said.

He was one stroke behind Hadwin's clubhouse lead when he rolled in a 34-footer for birdie at the 13th and regained the lead when he drained an 11-footer at the 14th.

A brilliant shot from a greenside bunker at the par-five 16th gave him another birdie look but Mickelson was unable to capitalise.

But he picked up another stroke with a 36-foot birdie putt at the par-three 17th before capping his round with a par.

"I gave myself a lot of chances," Mickelson said. "I missed a few short putts that I've been making for a while, but I also made a couple of long ones."

Hadwin fired his 65 on the Nicklaus course.

The Canadian is no stranger to strong performances in the Desert. He fired a 59 in the third round on the La Quinta layout on the way to a runner-up finish in 2017, and finished tied for third last year.

Hadwin, seeking a second PGA Tour title to go with his 2017 Valspar Championship crown, said his bogey-free day, which saw him hit 12 of 14 fairways and 16 of 18 greens in regulation, was "as stress-free as possible".

"A couple putts went in on the back nine and here I am having a chance again on Sunday," he said.

One-under through his first six holes, he birdied half of the remaining 14.

"I was playing one of the easier golf courses, so I knew I had to keep the pedal down," Hadwin said. "And, again, it was kind of a slow-ish start, but I've done that the first three rounds now and then just kind of caught fire midway."

Hadwin was one stroke in front of American Adam Long, who had two eagles in a nine-under par 63 at La Quinta. American Steve Marino was a further stroke back on 198 after a 67 on the Nicklaus Tournament course.

Mickelson said he'd stay aggressive when they return to the Stadium course on Sunday.

"It's a course you don't have to be perfect on," he said. "You have to hit a lot of good shots in certain spots. But if you miss it properly you can still play this course.

"I can come out and play aggressive and that's how I like to play."

Leading third-round scores on Saturday in the PGA Tour Desert Classic in La Quinta, California (par-72; USA unless stated):

194 - Phil Mickelson 60-68-66

196 - Adam Hadwin (CAN) 65-66-65

197 - Adam Long 63-71-63

198 - Steve Marino 66-65-67

199 - Michael Thompson 68-66-65, Patrick Cantlay 67-66-66

200 - Dominic Bozzelli 67-69-64, Jon Rahm (ESP) 66-66-68, Im Sung-jae (KOR) 71-65-64, Talor Gooch 67-67-66, J.T. Poston 68-68-64

201 - Scott Langley 70-65-66, Sean O'Hair 66-67-68, Joey Garber 68-64-69

202 - Jason Kokrak 71-65-66, Carlos Ortiz (MEX) 72-62-68, Sam Burns 68-66-68, Alex Cejka (GER) 66-68-68