MLS champions Seattle Sounders advanced to the Western Conference final after edging Dallas 1-0.

The Sounders progressed to their second successive conference decider thanks to Shane O'Neill, who settled Tuesday's contest in the 49th minute.

For only the second time this season and first since September 6, Seattle failed to record a shot on target in the opening half of a home fixture.

But O'Neill headed home his first goal for the club four minutes into the second half to break the deadlock and eventually move the Sounders to within a win of back-to-back appearances in the league showpiece.

The 27-year-old became the first player outside of Seattle's big three – Jordan Morris, Nicolas Lodeiro and Raul Ruidiaz – to score for the Sounders since Will Bruin on October 22.

Dallas came close to equalising just past the hour mark when Michael Barrios rattled the post, while Andres Ricaurte's follow-up attempt was thwarted by a goal-line clearance via Yeimar Gomez Andrade.

The Sounders will face either Sporting Kansas City or Minnesota United for a spot in the December 12 final.