60' Liverpool are pushing forward once again and finding a lot more space in behind United who can't get on the ball long enough to break out of their own half at the moment.
58' GOOD CHANCE! Thiago curls a great cross into the middle of the box and it's nodded on by Firmino. Milner runs onto it and tries to lift it over Henderson, but fires his effort high over the bar.
56' It's well-worked down the right by Liverpool and Salah pulls away from Shaw to lay it off to Firmino. He touches it onto the edge of the box, but none of his team-mates are there and Maguire clears his lines.
54' Rashford makes a driving run down the right, but he's closed down by Robertson so he squares it infield to Cavani. He flicks the ball into Greenwood's path, but he can't find a way past Williams to get in on goal.
52' Robertson has space to run into down the left again and Alexander-Arnold tries to switch play out to him. His first touch is poor though and he can't keep it in play to get a cross into the box.
50' Liverpool are pushing forward now as they try to react quickly to United's goal. Robertson plays his cross to the edge of the box, but it's over everyone's heads and Salah can't keep it in play on the right.
46' Liverpool get us back underway for the second half!
Both sides looked dangerous going forward in the first half, but Klopp will be expecting an improvement from his side in the final third as they haven't tested Henderson too often. United have had more shots on goal, but Alisson hasn't had much to do either. Solskjaer will expect his side to be much more clinical after the break.
It's level at the break between United and Liverpool. It was the visitors that opened the scoring when Firmino played in Salah and he brilliantly chipped his effort over Henderson and into the back of the net. Just eight minutes later, United were level when Rashford switched play out to Greenwood, who picked out the bottom corner. Pogba came close from a free-kick and Thiago made a good block to deny McTominay.
45' + 2' HALF-TIME: MANCHESTER UNITED 1-1 LIVERPOOL.
45' + 1' GOOD CHANCE! Rashford skips past two challenges as he cuts inside from the left and squares it to Greenwood. He lays it off to Pogba, who tries to curl his effort in at the near post, but he sends it just wide.
44' Shaw drills a cross into the six-yard box and Alisson comes off his line to push it away. He only gets it as far as McTominay on the edge of the box and he hits a low shot towards goal, but Thiago has dropped back and clears it for Liverpool.
43' CLOSE! It's Pogba that steps up to take the free-kick and he curls his effort around the outside of the wall to try and sneak it in at the far near post. It's just wide of the target, but it looks like Alisson had it covered anyway.
41' Alexander-Arnold plays the ball back to Alisson and Cavani is quickly closing him down. He gets rid of it quickly, but the pass to Fabinho is short and Greenwood comes across to get it, but he's caught by him.
39' McTominay wants too long on the ball and Jones nicks it off him. He plays it out to Robertson, and Henderson went to close him down as he cut it back from the byline. He's looking for Firmino at the far post, but Shaw heads it behind for a corner.
37' Another corner for United now and it's Shaw that swings this one in. He picks out McTominay this time, but he gets caught under the ball and his header loops high over the bar.
35' Shaw's free-kick is headed over by Williams, so the left-back goes across to take the corner. It's a good cross into Pogba on the edge of the box, but he heads his effort over the crossbar.
34' Salah brings the cross down on the right of the box, but a heavy touch gifts the ball to Pogba. He plays a throughball into Rashford, who is running into space down the left, and he wins a free-kick when Thiago brings him down.
32' Firmino has assisted Salah for 17 goals in all competitions for Liverpool; the most any player has set up another for the Reds under Klopp.
30' United are struggling to find a way out of their own half at the moment as Liverpool continue to press them high upfield. Wan-Bissaka looks like he has room to run into down the right, but Milner is quickly across to dispossess him.
28' Rashford makes a driving run down the left and slides his pass into Van de Beek from the edge of the box. He squares it across the box just as Alisson comes to close him down, but Thiago clears it in the middle.
24' Liverpool have a free-kick right on the edge of the box and it's Alexander-Arnold that steps up to take it. It's curling towards the near top corner, but there's not enough dip on it and it sails just over the bar.
22' Pogba loses out to Firmino and he plays a first-time ball into Jones after winning it off the Frenchman. The space opens up for him and he takes the shot from range, but it's straight at Henderson down the middle.
20' Liverpool are closing United down quicker when they don't have the ball now and Shaw can't find a way past Alexander-Arnold down the left wing, who then sets the visitors off on the counter.
16' Liverpool are pushing forward again and Salah switches play out to Milner on the right. He tries to take it past Lindelof, but a heavy touch takes it away from him and the defender sees it out for a goal-kick.
14' Cavani latches onto a loose ball and has a clear run to the Liverpool box. He has Rashford in support, but he chooses to play it out to Greenwood on the right. He wrongfoots Fabinho but fires his shot wide of the near post.
12' It's patient play from Liverpool at the moment as they try to play out from the back, but they're struggling to find a way in behind United. Milner tries a throughball into Firmino, but it's cut out by McTominay.
10' SAVE! Greenwood picks up the ball on the halfway line and makes a driving run down the right and into the box. It's a tight angle at the near post when he sends it across though and Alisson gets his foot to it.
8' Alexander-Arnold tries to play an early cross into the box, but he puts it behind Firmino through the middle. It looks like it might run through to Robertson on the far side, but Wan-Bissaka gets there first to clear his lines.
6' Maguire plays a long ball over the top to try and pick out Cavani's run between the two Liverpool defenders. There's too much on it for him though and Alisson rushes out of his box to head it away from danger.
4' Rashford makes a driving run into the box, but he can't find a way past Fabinho so he plays it out to Shaw on the left. He swings his cross towards Van de Beek at the near post, but Williams steps across him to intercept it.
2' Robertson switches play out to the right and Alexander-Arnold drills a low cross into the box. Shaw gets a foot on it in the middle but gives it to Wijnaldum on the edge of the box and he hits his shot, but the left-back blocks it.
1' Van de Beek gets the game underway for United!
The teams are out on the pitch now, with kick-off just moments away.
Liverpool have been eliminated from the FA Cup by United more than any other opponent in the competition's history (nine, including final defeats).
Jurgen Klopp makes four changes to the team that lost to Burnley last time as he brings in Rhys Williams, Milner, Salah and Firmino. Shaqiri, Oxlade-Chamberlain and Origi start on the bench.
Ole Gunnar Solskjaer makes five changes to his side after their win over Fulham on Wednesday, with Henderson, Lindelof, McTominay, Van de Beek and Rashford all coming in. Fernandes drops to the bench, along with De Gea, Martial and Fred.
LIVERPOOL SUBS: Sadio Mane, Nathaniel Phillips, Takumi Minamino, Konstantinos Tsimikas, Xherdan Shaqiri, Neco Williams, Divock Origi, Alex Oxlade-Chamberlain, Caoimhin Kelleher.
LIVERPOOL STARTING XI (4-3-3): Alisson; Trent Alexander-Arnold, Rhys Williams, Fabinho, Andy Robertson; James Milner, Thiago, Georginio Wijnaldum; Mohamed Salah, Roberto Firmino, Curtis Jones.
MANCHESTER UNITED SUBS: David de Gea, Nemanja Matic, Daniel James, Axel Tuanzebe, Anthony Martial, Juan Mata, Alex Telles, Fred, Bruno Fernandes.
MANCHESTER UNITED STARTING XI (4-2-3-1): Dean Henderson; Aaron Wan-Bissaka, Victor Lindelof, Harry Maguire, Luke Shaw; Paul Pogba, Scott McTominay; Mason Greenwood, Donny van de Beek, Marcus Rashford; Edinson Cavani.
It's been just one week since the teams last met and played out a 0-0 draw at Anfield. United come into this game having gone unbeaten in their last four in all competitions (W3 D1), which includes a 1-0 win over Watford to get through to this round. As for Liverpool, they've won just one of their last six in all competitions (D3 L2), which was a 4-1 victory over Aston Villa in the third round.
Hello and welcome to live coverage of the FA Cup fourth-round meeting between Manchester United and Liverpool at Old Trafford!