Zach Pfeffer struck a 93rd-minute winner as Philadelphia Union beat MLS Eastern Conference leaders DC United 1-0 at PPL Park tonight.

The second-half substitute pounced with a timely goal to bring an end to Union's four-game losing streak - and end United's eight-match unbeaten run in the process.

The best part of half an hour elapsed before either goalkeeper was tested, and it was United's Bill Hamid who had to be alert to keep out Vincent Nogueira.

Unperturbed, Union carried on in the same vein and Conor Casey was the next to test Hamid, but the visiting keeper was equal to it to preserve parity at the break.

It took 50 minutes for DC to fashion a meaningful attempt and the width of the woodwork denied Miguel Aguilar when he struck the post.

Buoyed by the near miss, the visitors came close again five minutes later when Kofi Opare headed Taylor Kemp's inch-perfect cross narrowly over the bar as the capital club grew in control.

The pendulum swung back in Philadelphia's favour, though, as Sheanon Williams forced Hamid into another smart save, before Sebastien Le Toux did the same on 73 minutes.

Hamid was moments away from earning a well deserved clean sheet but Pfeffer tapped home Fabinho's cross in the dying moments to snatch all three points.