The Seattle Sounders are already looking ahead to taking on either Liverpool or Real Madrid after achieving "immortality" by winning the CONCACAF Champions League.

The Sounders beat Pumas UNAM 3-0 at Lumen Field on Wednesday to complete a 5-2 aggregate triumph and finally deliver a first Champions League title for MLS.

Seattle are the league's third CONCACAF champions but first in the Champions League era after a series of heartbreaks for rival clubs.

Two goals from Raul Ruidiaz and a late clincher from captain Nicolas Lodeiro sparked scenes of mass celebration in front of a raucous, record crowd of 68,741.

Garth Lagerwey, the Sounders' general manager, gave Extratime his assessment: "Immortality. You get into sports for stuff people can never take away.

"This will be written down, it will be there forever. Hopefully it's the first of many."

Real Salt Lake, CF Montreal, Toronto FC and Los Angeles FC had each previously fallen at this final hurdle.

Now, for MLS, Lagerwey says, Seattle are "the symbol, we're the tip of the spear, we pushed through, we finally did it, we vanquished the demons".

"But everybody's welcome," he added. "We want a crowded mountaintop up here. We don't want to be up here by ourselves."

Playing just hours after Madrid had completed an epic semi-final fightback against Manchester City in UEFA's Champions League, Lagerwey could not help consider a Club World Cup clash with a European giant.

"We're going to play against Real Madrid or Liverpool in a real game for a trophy," he said, with Seattle's place in the tournament secure. "I feel like a little kid. This is the stuff you dream of."

The Sounders had already won two MLS Cups, a Supporters' Shield and four U.S. Open Cups, but this victory takes the club to another level entirely.

"I think we're going to become a global club now," the GM added.

"I've got to think my phone's got to start ringing once some people see what our fanbase, our building... it's as good a soccer environment as anywhere in the world. It just is. This is a pretty special place."