Two goals from Jamie Vardy edged Leicester ever closer to the 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.