The Portland Timbers punished slack defending to defeat Philadelphia Union 2-1 and reach the final of the "MLS is Back" restart tournament on Wednesday.

Goals in each half from US international Jeremy Ebobisse and Argentine veteran Sebastian Blanco sealed a deserved victory for Portland, who will now face either Orlando or Minnesota in next week's final.

The win leaves the Timbers eyeing their second piece of major silverware following their 2015 MLS Cup triumph.

But it was another frustrating tale of woe for Philadelphia, who dominated possession for long periods throughout the game but lacked the guile to unlock a well-organized Timbers lineup.

Portland, by contrast, always looked the most dangerous side going forward despite Philadelphia's dominance of possession.

Only a brilliant save by Philadelphia's Jamaican international goalkeeper, Andre Blake, denied Blanco an opening goal in the 11th minute, the Union shot-stopper diving low to his left to tip the South American's effort wide.

Portland did not have long to wait for the opener, though, when Diego Valeri's ensuing corner caused panic in the Philadelphia area.

The Paris-born Ebobisse punished slack marking from Kai Wagner and directed a firm downward header into the net past Blake from close range.

The Union's best early chance came when Jose Martinez's fierce long-range effort was blocked by Timbers goalkeeper Steve Clark.

At the other end, Portland continued to cause problems for Philadelphia with Ebobisse and Chris Duvall going close with shots from distance.

Portland looked to have preserved their advantage as half-time loomed, but Philadelphia were given a lifeline when Blanco was adjudged to have fouled Jamiro Monteiro in a clumsy challenge in the area.

But the Union's hopes of a morale-boosting equalizer went begging when striker Sergio Santos sent his spot-kick sailing over the bar.

Portland continued to carve out the better chances after the break, and both Valier and Jaroslaw Niezgoda should have done better when presented with time and space to shoot.

Portland finally got their second goal on 70 minutes and again it came from a corner following a save by Blake.

Dario Zuparic flicked on near the center of the penalty area and an unmarked Blanco headed in at the far post for 2-0.

Philadelphia rallied in the final minutes and pulled a goal back when substitute Andrew Wooten tucked away a rebound from close range after Monteiro's free kick in the 85th minute.

The Union thought they had grabbed an equalizer in the dying minutes, but Kacper Przybylko was ruled just offside after finishing Brenden Aaronson's pass.