MLS Cup holders Atlanta United defeated Philadelphia Union 2-0 on Thursday to advance to set up a last-four showdown with Toronto FC.

A superbly crafted first-half goal by Julian Gressel and a late strike from Josef Martinez settled an entertaining game at Atlanta's Mercedes-Benz Stadium.

Atlanta will now face Toronto FC in the final of the Eastern Conference Championship next Wednesday for a place in the MLS Cup final.

Atlanta, who won the MLS Cup last year in only their second season of existence, were made to work hard for victory against the third-seeded Union side.

Gressel's winner came after only 10 minutes, the 25-year-old German midfielder chipping in from just inside a crowded penalty area after clever interplay with Argentinian international Pity Martinez.

Philadelphia missed a golden chance to draw level in the 17th minute, when Brenden Aaronson was played into space by Sergio Santos.

But with the goal begging, Aaronson could only shoot directly at Brad Guzan in the Atlanta goal and the home side escaped.

The outcome remained in the balance until 10 minutes from time, when Venezuelan striker Josef Martinez latched on to a long ball from Gressel and rifled a shot into the top corner for 2-0.