Hibs maintained the pressure on third-placed Rangers with a fantastic first-half display at Easter Road.
The Hibees were fresh from their 5-1 victory against Falkirk which secured a place in the semi-finals of the Scottish Cup.
Tony Mowbray’s side were without Moscow-bound Garry O’Connor, who was sitting in the stand having agreed to join Lokomotiv Moscow in a £1.6million deal.
Hibs got off to the perfect start after just six minutes when Kevin Thomson fed striker Derek Riordan on the left. He cut inside two United defenders and drilled a low shot into the bottom corner past Craig Samson – job done.
United were almost on level terms just a few minutes later when a dipping long-range half-volley from ex-Hibee Grant Brebner grazed the top of Simon Brown’s crossbar. Samson then comfortably collected a Riordan free-kick after Gary Kenneth had fouled Chris Killen.
The visitors had another opportunity to equalise soon after, but midfielder Mark Kerr sent his effort wide from just six yards. And all of United’s work was undone when centre-back Alan Archibald headed Riordan’s teasing cross into his own net.
United looked to quickly get back in the game, but again shot themselves in the foot by conceding a third, as Hibs threatened to run riot.
Riordan’s long ball over the top looked harmless, but strike partner Killen was on to it in a flash and showed great physique to win the ball ahead of Kenneth. After outwitting the youngster, the New Zealand internationalist sent a shot from close range across Samson and into the far corner.
United boss Craig Brewster was evidently unimpressed with the opening half from his side and he withdrew David Fernandez and Stuart Duff for Colin Samuel and David Robertson at the start of the second period. The move sparked some urgency in the visitors and Barry Robson brought a smart save from Brown at his near post on 48 minutes.
David McCracken should have pulled one back from Robson’s free-kick but he glanced a free header wide, before Hibs’ Paul Dalglish brought out a flying save from Samson with a long-range effort at the other end.
United missed their best chance of the game when Robson picked out Trinidad and Tobago internationalist Samuel in space at the back post, but he could only prod the ball at Brown’s legs.
Riordan and defender Steven Whittaker were off target with Hibs efforts before a smart close-range save from Samson denied the onrushing Ivan Sproule with nine minutes remaining.
United battled on and claimed a consolation when 16-year-old substitute David Goodwillie forced home his first goal for the club two minutes from time, after first Samuel had hit the bar and then Robertson struck the post.
Hibs: Brown, Whittaker, Smith, Caldwell, Murphy, Stewart, Thomson, Glass, Riordan, Killen, Dalglish.