Updated

By Mark Lamport-Stokes

SAN DIEGO (Reuters) - American Ben Crane, helped by a couple of lengthy birdie putts, grabbed a one-shot lead midway through Sunday's final round of the San Diego Open.

While the expected last-day charge by three-times champion Phil Mickelson failed to materialize, Crane covered the front nine in a flawless, three-under-par 33 at Torrey Pines.

Birdies at the second, third and fifth on the challenging South Course lifted him to 14 under overall on another sun-kissed day on the California coastline.

Michael Sim of Australia, Crane's playing partner, was alone in second place, a stroke in front of Australian Robert Allenby, American Rickie Fowler and overnight leader Ryuji Imada of Japan.

Allenby was four under for the day after 11 holes while PGA Tour rookie Fowler had completed 10 holes and Imada nine.

World number two Mickelson, who began the day four shots off the lead, bogeyed the first three holes on the way to an untidy outward nine of two-over 38.

Crane, two strokes off the pace overnight, recorded his first birdie of the day at the par-four second where he struck a superb approach to three feet and knocked in the putt.

Two holes later, Crane picked up his third shot of the day, ramming in a 22-footer and pumping his right fist in celebration after the ball disappeared into the cup.

That gave him a two-shot cushion over the chasing pack at 14 under, until his lead was cut to one when Sim knocked in a four-foot birdie putt at the par-five ninth.

(Editing by Ed Osmond)