Dallas and Sporting Kansas City advanced in the MLS Cup play-offs after thrilling penalty shoot-out wins on Sunday.

Ricardo Pepi's 93rd-minute equaliser for Dallas cancelled out Jorge Villafana's opener for the Portland Timbers at Providence Park.

And after a marathon 16 penalties, Dallas prevailed 8-7 in the shoot-out as Jimmy Maurer saved from Villafana for the match-winning moment.

The opener came in the 82nd minute, Diego Valeri playing a pass to put Villafana in behind and the defender powered a finish into the roof of the net.

Valeri's assist was his 10th direct shot involvement in the match – four shots and six chances created – the most by a Timbers player in an MLS Cup play-offs match, according to Opta.

Just as Portland looked set to advance, Dallas equalised in the 93rd minute, Ricardo Pepi, 17, finishing a rebound after Timbers goalkeeper Steve Clark managed to save his initial effort onto the post.

It was the fourth time this MLS season that Portland had conceded a second-half stoppage-time equaliser. No other team has allowed more than two.

Valeri hit the post in the dying moments of extra time as the third penalty shoot-out through seven play-offs matches followed, already equalling the most traditional shoot-outs in a single postseason in MLS history.

After the first 15 penalties of the shoot-out were scored, Villafana was denied by Maurer, who sent Dallas through.

Los Angeles FC or the Seattle Sounders await Dallas in the Western Conference semi-finals.

Sporting Kansas City advanced after a thrilling penalty shoot-out win over the San Jose Earthquakes at Children's Mercy Park, where their encounter finished locked at 3-3.

Gianluca Busio looked to have won the encounter in additional time for Sporting, finishing after a wonderful flick from Khiry Shelton in the 91st minute to make it 3-2.

However, there was even more drama to follow, Chris Wondolowski heading in a 97th-minute equaliser from close range after Cristian Espinoza's cross.

Sporting goalkeeper Tim Melia would be the hero in the shoot-out, saving spot-kicks from Oswaldo Alanis, Jackson Yueill and Espinoza as Johnny Russell, Ilie and Shelton scored.

Melia became the first goalkeeper to shut out an opponent in a traditional penalty shoot-out in MLS Cup play-offs history.

In the Western Conference semi-finals, Sporting will face Minnesota United, who beat the Colorado Rapids 3-0 thanks to a brace from Kevin Molino.