Regis Le Bris' side trailed to Ephron Mason-Clark's goal late in the second half of the semi-final second leg.

But, with a penalty shoot-out moments away, Ballard headed home in stoppage-time to earn a 1-1 draw and spark wild celebrations from over 46,000 fans packed into the Stadium of Light.

Sunderland will face Sheffield United in the play-off final at Wembley on May 24.

United finished in third place, 14 points clear of fourth-placed Sunderland in the regular season, with both teams winning one against each other this season.

Sunderland's bid to return to the Premier League after an eight-year absence -- a dark period that has included a spell in the third tier -- remains alive.

But Le Bris' men will have to improve significantly on a nervous display that nearly gifted a place in the final to Coventry.

Languishing in 17th place until they were revitalised when former Chelsea and Everton boss Frank Lampard took charge in November, Coventry were desperately unlucky to fall short in their promotion bid as their 24-year Premier League exile continues.

Sunderland suffered five successive defeats coming into the play-offs, but they dug deep to reach the final in the most remarkable style.

Having won the first leg 2-1 at Coventry on Friday, Black Cats' staff were accused of moving the advertising hoardings two metres closer to the pitch than usual, reportedly to inhibit the visitors' long throws.

If that was meant to rattle Coventry, they nearly grabbed an immediate equaliser when Mason-Clark cut inside for a drive that was held by Sunderland keeper Anthony Patterson.

Jack Rudoni should have equalised from Mason-Clark's header just before half-time, but the midfielder poked over from inside the six-yard box.

It was a similar story in the second half as Coventry kept probing intelligently and Sunderland curiously opted to sit deep inside their own half.

Having defended tirelessly to keep Coventry at bay, Sunderland almost delivered the knockout blow through Trai Hume, whose volley was turned away by Ben Wilson at full stretch.

But, with time running out for Coventry, Mason-Clark hauled the Sky Blues level in the 76th minute.

Milan van Ewijk made a clever over-lapping run and whipped a pin-point cross into the Sunderland area for Mason-Clark to volley home from close-range.

Coventry should have settled the tie when Haji Wright headed wide from five yards in the final seconds of stoppage-time.

The tense extra-time period was almost over when Ballard stole the tie for Sunderland.

Stooping to meet Enzo Le Fee's corner with an ungainly header, Ballard flicked the ball in via the crossbar as the stadium erupted in a frenzied celebration.

Coventry's crest-fallen players slumped to their knees in despair.

For Sunderland, the promotion dream lives on in the most incredible fashion.