The Seattle Sounders guaranteed that a Major League Soccer club will contest the final of the CONCACAF Champions League after a 4-1 aggregate quarter-final victory over Mexico's Club Leon on Thursday.

Seattle, leading 3-0 from last week's first leg at home, advanced to a semi-final meeting with fellow MLS side New York City FC after securing a 1-1 draw in Thursday's second leg at the Estadio Leon.

Colombian veteran Fredy Montero effectively killed the tie off on the stroke of half-time, making no mistake from the penalty spot after Leon's William Tesillo upended Sounders midfielder Joao Paulo in the box.

That away goal meant Leon would need to score five second-half goals to overturn their aggregate deficit, a task that never looked likely against a well-organised Seattle defence.

Leon grabbed a late consolation goal with a thumping header from Fidel Ambriz in injury time.

Either Seattle or New York City will become the latest US team to attempt to end MLS's 22-year drought in the CONCACAF Champions League, the premier club tournament for teams from Central America, North America and the Caribbean.

The last MLS team to lift the title were Los Angeles Galaxy in 2000.

Mexican clubs have dominated the tournament in the years since, triumphing in every edition of the tournament since 2006.

Two Mexican teams, Pumas UNAM and Cruz Azul, will contest the other semi-final of this year's tournament.