A first-half thunderbolt from Ian Harkes sent Dundee United into the Scottish Cup quarter-finals as they defeated Partick Thistle 1-0 at Firhill.

The American’s sweet first-time strike from just outside the box settled a tight contest as United knocked out the Maryhill side for the second time in successive seasons.

The hosts dominated large periods of the game but they could not find the breakthrough as United, last year’s beaten semi-finalists, safely secured their passage into the last eight.

Thistle manager Ian McCall made two changes from his side’s 3-3 draw in Inverness on Wednesday night.

Alex Jakubiak made his first start since joining on loan from Dundee, with Cammy Smith dropping to the bench, while Stephen Hendrie slotted in for the suspended Tunji Akinola.

Meanwhile, Dundee United head coach Tam Courts opted to stick with the same starting XI that had impressively beaten Motherwell on Wednesday.

Partick recently drafted in a ‘pitch maintenance specialist’ following two recent postponements and the heavy pitch was a factor throughout after significant rainfall overnight.

The home side started brighter, putting together some slick moves despite the challenges of the surface.

Scott Tiffoney threatened with his weaving runs while Calum Butcher’s challenge needed to be inch-perfect as Jakubiak went through on goal.

It was the impressive Tiffoney who had the first effort on goal as he cut in from the left and aimed to curl into the top corner but United goalkeeper Benjamin Siegrist was equal to it, tipping it over the bar.

Brian Graham was the next to try his luck as the hosts dominated proceedings, with Ryan Edwards blocking his close-range shot after good work from Jakubiak.

United took the lead largely against the run of play in the 34th minute.

Liam Smith got away down the right and his dangerous cut-back was only partially cleared.

Harkes took it first time, rifling a left-footed effort into the far corner of the net to leave Thistle goalkeeper Jamie Sneddon with no chance.

The second period began in the same fashion as the first with the hosts on top and Kevin Holt’s curling shot forced a save from Siegrist before Tiffoney’s deflected strike was cleared before it reached the waiting Graham.

Tony Watt’s curling effort over the bar was as close as United came in the second half as Thistle continued to push for a leveller.

Cheered on by the home element of the 4,632 strong crowd, Smith drew another stop from Siegrist before fellow substitute Ross MacIver headed over but they were unable to find a breakthrough as United hung on to progress.