United's tense 2-1 victory over Liverpool earlier on Sunday moved them on to 69 points with seven matches remaining, two points clear of Arsenal, the overnight leaders. Chelsea are third on 65 points, but have a match in hand over the leading pair.
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Liverpool's 10th defeat of the season saw them slip back to sixth on 51 points and their chances of securing fourth and a place in the Champions League preliminary round are fading fast.
Liverpool struck first in glorious spring sunshine when an unmarked Fernando Torres headed in Dirk Kuyt's cross after only five minutes but their lead was shortlived.
United drew level seven minutes later after Javier Mascherano conceded a penalty for a foul on Antonio Valencia and, although Rooney's spot-kick was saved by Pepe Reina, the England striker pounced on the rebound to score his 33rd United goal of the season.
Korean Park scored the winner when he converted Darren Fletcher's cross from the right with a brave diving header after 60 minutes.
"It wasn't a classic, but it was so intense, I am sure no-one went for a cup of tea watching it on television that's for sure," United manager Alex Ferguson told Sky Sports.
"One situation changed everything," Benitez told reporters.
"I've seen three replays and the last one was very suspicious, seeing the replay and how he fell to the ground. There is maybe a contact but the way he fell down -- strange."
The victory strengthened United's challenge to become the first English club to win four successive titles. It would be their 19th crown, one more than Liverpool.
Their quest was aided when Chelsea failed to capitalise on their superiority at Blackburn to complete a miserable few days for Carlo Ancelotti's side after they were knocked out of the Champions League by Inter Milan on Tuesday.
