Needing a win to be crowned champions with two matches to spare, the magnitude of what Claudio Ranieri ‘s unchanged side were trying to achieve appeared to weigh heavily during a passive start and Anthony Martial capitalised by opening the scoring.
But captain Wes Morgan, one of the symbols of Leicester’s unlikely charge, headed a 16th-minute equaliser and the visitors will be disappointment not to have further punished a United side whose set-piece defending was flimsy throughout.
Leicester will emerge as champions at home to Everton next weekend if Tottenham fail to beat Chelsea on Monday, while any victory from the Foxes or slip up by Spurs will complete the remarkable story that Sunday’s action in Stretford left tantalisingly dangling.
United, who could not capitalise on a late red card for Danny Drinkwater, lost ground on Arsenal and Manchester City in the race for a top-four spot but edged ahead of West Ham into fifth.
The visitors barely ventured beyond their own half before United took an eighth-minute lead – Antonio Valencia, in for Timothy Fosu-Mensah at right-back, picking out Martial for the unmarked France international to thump his ninth league goal of the season through Kasper Schmeichel’s legs.
Shinji Okazaki headed over at the near post from a Riyad Mahrez cross following a Leicester set piece and United did not heed the warning as Morgan muscled past Marcos Rojo to plant a header beyond David De Gea from Drinkwater’s floated free-kick.
Schmeichel, playing on the ground where his father Peter became a United icon for the first time, denied Jesse Lingard with sharp saves either side of the equaliser as Leicester’s defence lacked the solidity of recent months.
City right-back Danny Simpson – notable by his absence on the United opener – escaped punishment for grappling with Lingard as the United star bore down on goal.
But Leicester ended the half strongly, as Drinkwater had an effort deflected behind before Morgan, again making a mockery of Rojo’s attempts to mark him, headed over.
Okazaki just failed to get a decisive touch after Simpson burst forward to cut the ball across the six-yard box and Leonardo Ulloa had a low drive deflected behind amid an excellent start to the second period from Leicester.
PFA Player of the Year Mahrez embarked on a trademark jinking run in the 71st minute and De Gea awkwardly punched his resulting shot to safety.
United belatedly posed some second-half questions as the livewire Martial almost saw his low cross turned in by a sprawling Morgan, while Chris Smalling headed against the outside of the post from a deep Wayne Rooney cross.
Ranieri’s side finished with 10 men as Drinkwater collected a second booking for bringing down United sub Memphis Depay on the edge of the box.
The England midfielder will miss out next Saturday, when Jamie Vardy is expected to return from a ban of his own and by which time a memorable piece of history might already belong to Leicester.