Last update on. From the section Scottish Premiership
Ian Harkes's acrobatic diving header brought United level in the first quarter
Celtic's troubles in the Scottish Premiership continued, as Dundee United won a point.
Liel Abbada nodded Celtic in front, but the visitors soon equalized with a fantastic Ian Harkes header.
Three times Albian Ajeti failed to score, and Albian Ajeti missed a goal. United was denied a penalty claim when Nicky Clark was thrown out.
Celtic are currently in sixth place after dropping their first points at home and three away defeats.
They trail Rangers by six points and United by one point. United's youthful side impressed and withstood an early barrage to win their first Celtic Park point in eight years.
Celtic suffered injury concerns after Josip Juranovic's first-half defeat. James McCarthy was replaced at the break following a Jeando Fuchs challenge.
Although Celtic were in the worst league season start in 23 years, this could have been attributed to their away form. This contrasted starkly with their home win record of three consecutive wins.
United broke that record and took advantage of Celtic's ineptness in a frenetic first-half brimming with incident.
Celtic gained momentum early - Juranovic had his shot blocked by Benjamin Siegrist, and Ajeti was heading too high. This was before their wingers combined to score the breakthrough. Jota cut in to the left and crossed over to swing over a cross that was met with a thunderous Abada header at his back.
United was motivated by the setback and were back on track in no time. Finnish winger Ilmari Niskanen defeated Anthony Ralston down to the left, and Harkes converted his whipping delivery with a diving header.
Both sides were right to be upset that they did not have a lead at half-time. United, whose high-press agitated Celtic's defense throughout the match, were puzzled by Kevin Clancy's decision to not award a penalty after Cameron Carter-Vickers sent Clark sprawling.
Ajeti, at the other end, blazed through an unguarded net of four yards. David Turnbull hit a 20-yarder against the bar. Ajeti was guilty of another serious miss in the second period, going wide from six yards.
Ange Postecoglou's men increased the pressure after the break but lost their conviction in the last third.
Jota was their best hope of a win, and nearly got it with a last-minute dipping drive off the line. Tom Rogic made the goal frame shake with a header from Jota’s knockdown. Celtic's rally was short.
United, however, was determined to defend and remained a threat on the counter-attack. Niskanen was just inches from reaching the far corner with a curling strike. The visitors could have won a dramatic win, but substitute Louis Appere saved Joe Hart's life with a near-post drive.
Appere was then stopped by a brilliant Carl Starfelt tackle. The end-to-end action continued for the last seconds.
Ian Harkes is the Man of the Match
United scored a goal with brilliant skill and a superb performance by the midfielder to earn a point
What have we learned?
Celtic cannot get their key men back fast enough. In a chaotic display, Callum McGregor's leadership and Kyogo Furuhashi's finishing prowess were both badly missed.
Ajeti failed to win the front. Although the striker won't offer Kyogo's movement, he should have converted at most one of the obvious opportunities.
United, to a woman, were outstanding. Thomas Courts' young side featured Kerr Smith, 16, at centre-back. This caused all kinds of problems for the hosts.
Courts now has the Tannadice men in fifth place after beating Rangers and holding Celtic. There was also a win over Dundee in the derby.
What were they saying?
Ange Postecoglou, Celtic manager: "Obviously disappointed by the outcome but I believe it's our approach that is exactly what our fans want to see."
"We had a lot of opportunities, but we didn't seize them. Sometimes football works that way. We score four to five goals on another day."
Thomas Courts, Dundee Utd's head coach: "It [the penalty claims] was very legitimate. It was very disappointing. We saw it at half-time.
"This was a huge task for my players – three games in seven days, plus the emotion of Dundee derby – but they were exceptional. They are truly a credit to me.
Celtic face a difficult task against Bayer Leverkusen, an in-form German team. They will be playing in the Europa League group stage on Wednesday (20:00 BST), followed by a Premiership game at Aberdeen on Sunday (12:00).
United will be looking to win four league games without defeat when they play Ross County Saturday (15:00).
Benjamin Siegrist was the player of the match with an average 8.42 Celtic Celtic Celtic Celtic Celtic.
Dundee Utd Dundee United Celtic Avg squad number 11 Player named Abada Average ranking 3.86 Squad numbers 15 Playername Hart Playername Jota Average ratings 3.35 Squad numbers 4 Playername Starfelt Playername Average Rating 3.34 Squad Number 10 Playername Harkes Playername Harkes Playername Harkes Average rate 8.39 Squad numbers 66 Playername Harkes Playername Harkes Playername Harkes Playername Harkes Playername Harkes Average Rating 8.27 Squad Number 27 Playername Appr Playername Edwards Squad number 10 player name Clark Playername McMann Squad size 22 Squad name McMann Playername McMann 7.95 Playername Freeman 7.95 Playername McMann Squad No.22 Playername Freeman