The Red Devils on Monday night defeated a spirited FC Copenhagen side 1-0.
The only goal of the match came in the 97th minute of play, after both teams failed to score within regulation time.
Inter Milan emerged as the second semi-finalist in the other game of the night.
Nicolo Barella and Romelu Lukaku gave the Serie A side a two-goal lead within 23 minutes.
Although Kai Havertz pulled one back before the break, the match ended without any more goals.
Inter await the winner between Basel and Shakhtar Donestk.
