Canberra United have beaten Sydney FC 1-0 in an action-packed top-of-the-table Westfield W-League clash with at Leichhardt Oval on Saturday.

The victory, Canberra's first against the Sky Blues, came courtesy of an Ashleigh Sykes goal on 19 minutes.

Sydney swamped forward in the second half, inspired in part by the half-time introduction of teenage star Caitlin Foord, only for United's Westfield Matildas goalkeeper Lydia Williams to provide an impenetrable last line of defence.

Canberra though weren't without opportunities to extend their lead, with the team from the nation's capital looking particularly dangerous on the break.

Despite the non-stop second-half action, the pivotal moment of the game was the first genuine goalscoring opportunity.

Canberra sharpshooter Michelle Heyman managed to get goalside of the Sydney defence and her mishit shot ran across the face of the goal where Sykes easily converted.

The first half wound to a close with chances at either end but Sydney's Heather Garriock and Canberra's Taryn Hemmings both pushed their efforts narrowly wide.

The second period commenced in dramatic fashion with goalmouth action at either end, setting the tone for the remainder of the contest.

The impact of Foord was immediate with the 2011 FIFA Women's World Cup young player of the tournament denied by an excellent Williams save with virtually her first touch.

Servet Uzunlar then cracked a long-range effort against the crossbar with Sydney seemingly revved up by the half-time directions.

At the other end Sky Blues defender Danielle Brogan was then forced to clear off the line from Heyman's shot to conclude a remarkable five-minute spell.

Midway through the second stanza Williams made a great save to deny Renee Rollason in what proved to be a portent of things to come.

Canberra's US import Taryn Hemmings narrowly cleared the crossbar with an effort from distance but generally the visitors were forced to rely on long-range shots or counter-attacks.

It was then the turn of Sydney substitute Brittany Whitfield to be denied at point-blank range by Williams.

Sykes burst upfield from the ensuing play to fire narrowly wide but the narrative of the match was played out with the final chance.

Foord advanced on goal with only Williams blocking the path to an equaliser, but again the United shot-stopper proved unbeatable as Canberra took a handy lead at the top of the ladder.