Image source, Reuters

The game has become pretty stretched, which is promising for those who want this to be settled in extra-time.

But no-one has yet showed the cool head and mental freshness to make the right decision when it matters.

Sunderland are first to make use of their fourth substitution in extra-time.

Veteran midfielder Grant Leadbitter makes way for number nine Charlie Wyke, who will be a presence up top.

It's Sunderland on the front foot, moving the ball around and trying to probe Pompey.

The pace has unsurprisingly come out of the game, somewhat, but it remains exhilarating to watch.

Referee Dean Whitestone has his comfort break and gets extra-time under way at Wembley.

Both sets of players shake their legs out as they go into unknown territory - who has the most left to give?

Portsmouth and Sunderland can now use a fourth substitute if they wish.

What are we making of this Checkatrade Trophy final, then? And who will go on to win it?

Keep the comments coming using #bbcefl on social media.

Image source, Rex Features

As we wait for extra-time to begin, how about this...

A confirmed Wembley crowd of 85,021 breaks the record for any final in the competition's history, surpassing the 80,841 who saw Wolves beat Burnley in 1988.

We take our hats off to Portsmouth and Sunderland fans.

Well, not really full-time as we're going to extra-time!

Pompey's Gareth Evans had to hurriedly clear Denver Hume's dangerous cross but they hold firm and we've got another 30 minutes to come.

Sunderland had been in total control but their opponents were incredibly strong in the second half - levelling through Nathan Thompson - and deserve to still be in with a chance of winning this trophy.

Into the last 60 seconds of normal time - Sunderland on the ball.

Can they create anything?

Adam Williams
BBC Sport at Wembley

Sometimes you can dread extra time in a game, but not this one.

It really has been the proverbial game of two halves with a couple of brilliant goals to go with it.

Plenty of shredded nerves already for both sets of supporters without another 30 minutes to contend with.

Oliver Hawkins heads the ball down for Gareth Evans in the box, but his shot is blocked by Grant Leadbitter and out for a Pompey corner.

Matt Clarke heads the resulting set-piece wide.

Image source, Reuters

Sunderland keeper Jon McLaughlin eventually catches the free-kick.

We're into four minutes of stoppage time.

Tempers flaring at Wembley - Aiden McGeady loses the ball to Pompey scorer Nathan Thompson and hacks him down in frustration.

The Sunderland man also shows dissent and goes in the book.

Chance for Portsmouth to get the ball in the box...

Reece James has been struggling with injury for a while - he comes off for Sunderland, replaced by local youngster Denver Hume.

A big occasion for him.

Will Pompey's momentum take them to the trophy or can Sunderland find a second wind to clinch it?

The team in red and white have the ball at the moment but lack the penetration they showed in the first half.

Reece James puts in a cross and Lee Brown heads out for a Sunderland corner.

Gareth Evans almost scores a memorable equaliser for Portsmouth!

He lobs Luke O'Nien in the middle and drives forward before striking low, hard and just wide of the post.

Sub Evans has three goals from four shots on target in the Checkatrade Trophy this season, so is one to watch.

Lynden Gooch has come on full of energy and adrenaline, bursting past players and confronting one of two Pompey players off the ball.

His Sunderland team-mate Will Grigg has been quiet - he's off, with Max Power on to turn things up a notch.

Chris Wise
BBC Radio 5 Live at Wembley

The noise and belief is with Portsmouth at the moment. Those in blue are waving thousands of flags in the hope that the energy they create is reflected in their team's performance. There is an element of symmetry at the moment.

Sunderland supporters are looking slightly nervous. Actually, the sort of cutaways that would make for a good edit on any forthcoming documentary.

Nathan Thompson has just put in a crunching challenge on Sunderland's Luke O'Nien - one for the 'firm but fair' category.

Jack Ross brings on Lynden Gooch for Lewis Morgan, who, like Aiden McGeady and Sunderland as a whole, has faded since the break.

Image source, Reuters

This game possibly sums up why Sunderland aren't certainties for promotion from League One.

Despite their obvious quality they haven't been able to put a full 90-minute performance together, which explains the number of draws they've had this season.

Pompey are still pushing and their opponents need to show composure on the ball.