كتب : Omar AbdelAziz
United reached 84 points at the summit, three ahead of Chelsea, who still have Newcastle on Monday.
The Red Devils need a win against Wigan next week to secure the title, as they boast a far more comprehensive goal difference over their Champions League final opponents Chelsea.
Alex Ferguson's side needed no time to prove their dominance over the mid-table Hammers as Cristiano Ronaldo grabbed a brace inside the first half-hour.
The formidable Portuguese opened the scoring on three minutes when he cut inside the West Ham area before firing home a low shot past Robert Green.
Man of the season Ronaldo scored his 40th goal of the season 20 minutes later, this time with a fortunate close range finish.
Only two minutes later, Carlos Tevez scored a super strike against his former club, sending a 25-yard thunderbolt into the roof of Green's net.
The action continued as Dean Ashton pulled one back for West Ham two minutes later when he scored a contender for goal of the season with a magnificent overhead kick.
Eight minutes before the break, United were reduced to ten men as Luis Nani saw red for headbutting Lucas Neill.
However, the sending off hardly affected United, who scored the fourth on the hour mark, thanks to a deflected Michael Carrick shot.