One more point will secure place in Champions League
15 minutes of the first half.And the hosts found themselves a goal down moments before half-time after Tim Fosu-Mensah brought down Michail Antonio with a late lunge to concede a free-kick.
Hammers skipper Mark Noble slid the free-kick to Declan Rice, whose sliced shot was blocked by the arms of Paul Pogba in what was a blatant penalty.
Antonio stepped up to take the resulting spot-kick and calmly rolled the ball into net for his eighth goal in his past six games, with De Gea diving the wrong way.
With Rice’s shot way off target, it was a needless penalty to concede, Pogba covering his face immediately after to feign injury, but he was fooling nobody. United were level five minutes after the restart through Greenwood, who combined with Anthony Martial before applying a clinical finish for his 17th goal of the season on his 50th appearance for the Reds.
De Gea pulled off a fine save just after the hour, tipping a deflected Jarrod Bowen shot over the bar as West Ham looked for a winner.
For United, now the focus shifts to Sunday and the Champions League shoot-out at the King Power Stadium.
MAN UTD (4-2-3-1): De Gea 7; Fosu-Mensah 5 (Wan-Bissaka 46, 6), Lindelof 5, Maguire 6, Williams 6; Matic 6, Pogba 5; Greenwood 7, Fernandes 6, Rashford 5 (Ighalo, 84); Martial 7. Goal: Greenwood 51.
WEST HAM (4-2-3-1): Fabianski 6; Johnson 6, Diop 7, Ogbonna 7, Cresswell 6 (Masuaku, 75); Rice 7, Soucek 7; Bowen 7 (Yarmolenko, 90), Noble 7, Fornals 6; Antonio 7 (Haller, 77). Goal: Antonio 45 pen.