Louis van Gaal said Manchester United’s inability to score goals is a problem as they slipped to their sixth 0-0 draw of the season in all competitions.
United have now drawn five of their last nine games by the same 0-0 scoreline and their tally of four in the Premier League is the most of any team.
A well organised and disciplined West Ham restricted Van Gaal's men to little attacking openings in the stalemate on Saturday and should have won the game having created four clear cut chances.
United have scored one goal or less in nine of their 15 Premier League matches this season and strikers Anthony Martial and Wayne Rooney have only notched five goals between them in the league.
Rooney was missing with an ankle injury but Martial, who hasn't scored in seven league games, and Marouane Fellaini both wasted good openings in the second half as United were booed off by a section of the home fans at full-time.
"We saw a very good match where West Ham were very organised," said van Gaal.
"Nevertheless, we have created chances. We need to score. We must score. But we didn't score and that's our problem. We can be pleased with our second half performance.
"The first quarter of the match we were very dominant and created chances, but you have to finish them because that is football - you have to score goals, otherwise you can't win. You need composure and luck.
"The most important thing is that we're dominant and creating chances. The other aspect we have to improve a lot as we don't score.
"We are showing good organisation and keeping clean sheets. That's very good. But we need to score. I know that. The fans the know that. The players know that. When you don't score from a metre out, you can say it's unlucky, but you have to score those kind of chances."