Jamie Vardy's double edged Leicester ever closer to the the Barclays Premier League title as Sunderland's survival hopes suffered a major blow.
Vardy's 66th-minute and stoppage-time strikes - his 20th and 21st of the season and his first in seven games for his club - secured three hard-fought points in a 2-0 win at the Stadium of Light on a day when the home side grudgingly surrendered a four-game unbeaten run in front of a crowd of 46,531.
Indeed, it might have been very different had Foxes keeper Kasper Schmeichel not managed to react in the nick of time to keep out Fabio Borini's deflected shot as the first half drew to a close.
Claudio Ranieri's men will head into next Sunday's home clash with West Ham knowing their fate remains firmly in their own hands, while Sam Allardyce will send out his team at Norwich the previous day acutely aware that defeat there could prove all but fatal.
The game kicked off with 42 points separating the sides with the Foxes looking to seal the most unlikely of title charges and the Black Cats desperately seeking a fourth successive great escape, but there was little to choose between them during a high-octane first half.
The visitors started on the front foot as Sunderland defender Younes Kaboul found himself under intense pressure from front two Vardy and Shinji Okazaki with the England international heading wastefully wide after meeting Danny Simpson's inviting 12th-minute cross.
Captain Wes Morgan was equally profligate three minutes later after being picked out from a corner by Christian Fuchs, but as the home side settled, it was they who started to make an impact.
Borini fired into the side-netting after taking a poor first touch from Jan Kirchhoff's through-ball, and Kaboul powered a header over from the influential Wahbi Khazri's 35th-minute cross.
Both teams had penalty appeals waved away, Sunderland after Patrick van Aanholt's cross struck Robert Huth's arm as he slid in and the visitors when Riyad Mahrez's shot thumped into Kaboul's elbow, but Allardyce's men very nearly snatched the lead two minutes into stoppage time.
Borini found space on the right side of the penalty area and drilled in a shot which momentarily wrong-footed Schmeichel after clipping Morgan, but the keeper did well to block with his legs.
The Italian came agonisingly close to breaking the deadlock when he drilled a rising 51st-minute drive inches wide, but Leicester responded with Okazaki firing over after exchanging passes with N'Golo Kante and keeper Vito Mannone taking advantage of Danny Drinkwater's heavy touch from Vardy's teasing 54th-minute cross to intercept.
They eventually got their noses in front with 24 minutes remaining when for once, Kaboul lost Vardy as he set off in pursuit of Drinkwater's long ball, and his finish was unerring.
Substitute Jack Rodwell passed up a glorious opportunity to level with eight minutes remaining after Van Aanholt's shot had been blocked into his path 10 yards out, and although Vardy missed one chance to wrap up the win at the death from Drinkwater's pull-back, he did so deep into stoppage time as he out-muscled Van Aanholt and rounded Mannone before steering the ball into the empty net.
TWEET OF THE MATCH
"Just missed #vardeys goal. Asked Mrs T what was it like. Answer. Like yours should have been against France. Will they ever forget ???? #lcfc" - Former England midfielder Geoff Thomas reacts to Vardy's opening goal.
Vito Mannone: 6
DeAndre Yedlin: 7
Younes Kaboul: 7
Lamine Kone: 7
Patrick van Aanholt: 6
Jan Kirchhoff: 7
Lee Cattermole (Capt): 6
Yann M'Vila (Rodwell, 68 mins): 6
Wahbi Khazri (N'Doye, 68 mins): 7
Fabio Borini (Lens, 76 mins): 7
Jermain Defoe: 6
Jack Rodwell: 5
Dame N'Doye: 5
Jeremain Lens: 6
Kasper Schmeichel: 7
Danny Simpson: 7
Wes Morgan (Capt): 7
Robert Huth: 6
Christian Fuchs: 6
Riyad Mahrez (Gray, 81 mins): 6
Danny Drinkwater: 8
N'Golo Kante: 7
Marc Albrighton (Amartey, 84 mins): 7
Shinji Okazaki (Ulloa, 62 mins): 7
Jamie Vardy: 7
Leonardo Ulloa: 6
Demarai Gray: 7
Daniel Amartey: 6
As the game opened up, Danny Drinkwater was the man who took advantage, setting up the decisive goal with a superb pass and creating another glorious opening for match-winner Jamie Vardy at the death.
MOMENT OF THE MATCH
In a contest of few clear-cut chances, Vardy converted the most inviting with aplomb, running on to Drinkwater's 66th-minute through-ball to slide his shot past keeper Vito Mannone and put the visitors ahead.
VIEW FROM THE BENCH
Sam Allardyce once again could not fault much of what he saw from his players, but was left - and not for the first time - bemoaning their failure to take the chances which came their way. Claudio Ranieri will have been delighted with the way his side maintained their standards, remaining solid at the back and clinical in attack.
MOAN OF THE MATCH
Substitute Jack Rodwell will be haunted by the 82nd-minute miss from which he should have dragged Sunderland level.
WHO'S UP NEXT
Norwich v Sunderland (Barclays Premier League, Saturday April 16)
Leicester v West Ham (Barclays Premier League, Sunday, April 17)
Leicester midfielder Drinkwater told Sky Sports there is still work to be done, but his facial expression suggested the Foxes players now firmly believe the title is theirs to lose.
"We've got a few games left. It's a step but a very big one," he said. "If this puts more pressure on them (Spurs) then perfect but I can't see Tottenham putting too much on this. It's up to them now. The fans here are brilliant, and credit to the lads we deserved that."
As Leicester's fairytale continues, Vardy thanked the Sunderland fans for showing their appreciation at the end of the match.
"Coming off the Sunderland fans were clapping us as well which is brilliant," he said. "It was a great game, we knew it would be tough but managed to grind it out. It's a step closer to possibly winning the league. We'll enjoy this for the rest of the day and then get back to training for the next week."
Sunderland boss Allardyce said his side's performance was down to the situation they have put themselves in earlier in the season.
"We were nervous today because of how big the game is. It's a legacy of not picking up the points when we should have done. That caused us to do the wrong things to try and get back in the game," he said.
"I thought we were very poor after (the opening goal). Jack Rodwell should have scored, you can't get a better chance than that and it would have put it at 1-1, then in the final five you have to throw caution to the wind.
"Norwich was always going to be big. There would be less pressure if we had won but today was always going to be difficult to win. We are under extreme pressure that we have to make sure we handle."
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