A Lys Mousset strike earned United a deserved point in the capital after a 1-1 draw against West Ham United.
A stirring second half showing from the Blades saw Chris Wilder's side come from behind after a Robert Snodgrass opener, to level thanks to a low strike from the Frenchman, who bagged his second goal in as many games.
The Blades had the better chances in a first ever meeting with the Hammers at the London Stadium, as Wilder's side stay unbeaten on the road this season.
Wilder made one change to the side which beat Arsenal as striker Callum Robinson replaced Mousset in attack.
In a quiet opening 10 minutes, the hosts threatened briefly when a low cross from deep by Snodgrass just eluded the stretching Andriy Yarmolenko, whilst Dean Henderson punched clear a dangerous Snodgrass centre from the near side a few moments later.
United showed some intent on 19 minutes when Robinson played David McGoldrick in down the right, but as the ex-Preston striker piled into the area looking for a centre, his compatriot sent the cross too deep and the home side cleared.
The first attempt of note arrived on 23 minutes. Felipe Anderson picked the ball up midway inside the United half, and after advancing forward he accepted the invitation to shoot, but Henderson wasn't troubled as the Brazilian's effort flew over.
United gradually started to grow into the contest and were presented with the best opening on 28 minutes.
In the build-up, Issa Diop was booked for a late challenge on McGoldrick, as George Baldock's cross was turned behind for a corner. John Fleck delivered from the far side towards Jack O'Connell who rose to nod down into the direction of McGoldrick. The Irishman flicked an effort towards goal from six yards out but home 'keeper Roberto made a block, and a ruck of home shirts then denied John Lundstram with the follow up.
McGoldrick then threatened on the counter for United but his surge into the West Ham half was halted by Pablo Zabaleta. From the resulting free-kick, McGoldrick peeled away towards the back post to meet Fleck's cross, but his header was comfortably held by Roberto.
On 41 minutes United created another half chance. Good work by Ollie Norwood and McGoldrick helped to develop the attack, as O'Connell then crossed on the overlap into the near post where Lundstram turned his effort wide.
A minute later and United were presented with another opportunity. Lundstram's cross from the right was totally missed by the flying Roberto, but the 'keeper's presence in front of Robinson was enough to distract the striker who mis-directed his header with the goal empty. Enda Stevens' attempted follow up was then deflected wide.
Against the run of play, the hosts then took the lead with a minute of the half remaining. A long punt forward by Roberto was headed clear only as far as Yarmolenko whose first-time pass put Snodgrass through, and he drilled the ball low beyond Henderson.
The Blades countered at the start of the second half through Fleck who drove into the heart of the home defence. After feeding the ball wide to Lundstram, his low centre arrowed into the direction of Robinson, but the Hammers made a crucial clearance in the six-yard area.
At the other end, Norwood made a terrific block from a Yarmolenko effort as the game started to open up.
United were denied again with another good opportunity after a clever flick from Lundstram at the by-line released Fleck who crossed the far post. Baldock was waiting and after steadying himself with a touch, his fierce drive was somehow kept out by Roberto who knew little about the save.
Wilder then threw Sharp into the fray, replacing Robinson 10 minutes into the second stanza.
The game was now end-to-end, with United having Henderson to thank for keeping it at 1-0 after a low save to deny Anderson as West Ham almost profited from Norwood being dispossessed.
Baldock saw yellow for a late challenge on Declan Rice just before the hour, becoming the first United name into the book.
The chances kept on coming for United, as Baldock fired wide after great work by Fleck and McGoldrick. Fabian Balbuena was also booked for an attempted foul on Fleck in the build-up.
Wilder made another attacking change on 64 minutes, replacing Norwood with Mousset.
Sharp had the ball in the net from Chris Basham's cross, but the flag had long since gone up rightly for offside.
United were on top and finally the Blades' pressure told with a well-deserved equaliser on 69 minutes. The Blades kept alive a cross from the right from Baldock, and as the hosts failed to clear, Stevens headed the ball down for sub MOUSSET who volleyed accurately into the bottom corner for his third goal of the season.
West Ham responded with Henderson quick to smother an effort from Aaron Cresswell at the back post, which was quickly followed by a save from distance from the boot of Rice.
The Hammers missed a golden chance inside the final 10 minutes as a cross through the six-yard area found Snodgrass who hit the outside of the post at full stretch.
Late on Stevens saw yellow just after Yarmolenko had fired wide with a shot from distance.
West Ham: Roberto, Zabaleta, Balbuena, Diop, Cresswell, Rice, Noble (Fornals 78), Snodgrass (Ajeti 86), Yarmolenko, F. Anderson (Lanzini 66), Haller.
Unused: Martin, Fredericks, Ogbonna, Sanchez,
Blades: Henderson, Baldock, Stevens, Fleck, O'Connell, Basham, Lundstram, Robinson (Sharp 54), Egan, Norwood (Mousset 63), McGoldrick (Bešić 80)
Unused: L. Freeman, McBurnie, Jagielka, Moore.
As it happened...
The action is underway...
Early corner for the hosts, but referee Coote spots a foul in the box and the Blades are awarded a free-kick
Stevens is forced to clear behind at the expense of another corner. Snodgrass sees his inital delivery cleared, but Egan heads behind to give another opportunity, which the Blades clear
United break down the right, McGoldrick finds plenty of space, but overhits his cross, from a promising position, with Robinson lurking.
It was West Ham on the offensive, forcing a couple more corners in quick succession, but through O'Connell and then Baldock, the Blades cleared without too much alarm.
Moments later, Anderson cut inside from the left and bent a dipping effort just over, with Henderson at full stretch.
So close for the Blades. After playing a role in winning the corner, McGoldrick is denied from point blank range by Roberto after O'Connell's header down from Fleck's inswinging corner.
McGoldrick again heavily invovled. This time he sees his header saved by Roberto, having earlier won a free-kick after he seized possession following a mistake by Rice.
United were continuing to grow into the game, but Robinson couldn't direct his header at goal with Roberto at full stretch, before Stevens saw his strike defelcted behind on the rebound.
Goal for West Ham, against the run of play. Yarmolenko plays in Snodgrass from Roberto's long kick forward and he slots it past an advancing Henderson.
Harsh on the Blades, who have had two or three good chances, but it's West Ham who lead at the break.
The second-half is underway here at the London Stadium, United looking to get back on terms.
Early corner for West Ham, but it's the Blades who break quickly, only for Zabalaeta to cut out Lundstram low cross.
This time, it's the home side who counter. Anderson gets the better of Basham from Noble's ball forward, but Haller hesitates and Yarmolenko's effort is blocked.
The opening minutes of the second-half were open to say the least. But the home side manage to keep out Baldock's shot from inside the box, with Fleck and Lundstram involved in the build-up.
First change for the Blades, as Sharp replaces Robinson.
Henderson denies Anderson, after the West Ham man had robbed Norwood and combined with Yarmolenko to create a clear sight of goal.
Baldock is booked having caught Rice in a 50/50 challenge.
Balbuena is booked for a nasty lunge on Fleck, referee Coote plays advantage though and Baldock fires wide after a pass from McGoldrick.
Mousset is introduced as he replaces Norwood, a switch that sees Sharp take the captain's armband.
United have the ball in the net through Sharp, only for the assistant referee to have flagged moments earlier with Basham in an offside position.
GOOALLLLLLLLLLLLLLLLLL! The Blades are level and it's that man Mousset again! The substitute volleys into Roberto's bottom corner, to deservadly restore parity at the London Stadium...MOOOSE!
It's Henderson to United's rescue again, with the goalkeeper out quickly to deny Cresswell who had found space in the box from Yarmolneko's dink.
In West Ham's next attack, Henderson pushes away a stinging effort from Rice.
West Ham make another change, with Fornals replacing skipper Noble. Earlier Lazzini took the place of Anderson.
Big let off for the Blades, as Snodgrass slides an effort into the back post, with Henderson stranded.
United's final change sees a Premier League debut for Besic, with McGoldrick the man to make way.
United force a couple of late corners, but Sharp loses possession from the second with the Blades trying to run down the clock.
Four minutes of added time are then signalled.
The home crowd are up, but Yarmolenko's left-footed effort curls wide, with Henderson having it covered.
Stevens is booked having halted the progress of Haller.
It's over at the London Stadium, it finishes all square. An excellent and deserved point for the Blades.
Chris Wilder's travelling army are in fine voice as the players head over to thank them for their continued backing.
United remain unbeaten away from home since the defeat at Swansea City in January.