Macarthur tightened their grip on a top-six spot in the A-League courtesy of a 2-1 win at lowly Western United.

The Bulls look set to secure a finals berth in their maiden campaign, with Ante Milicic's side boasting a four-point gap to seventh-placed Wellington Phoenix, who they play on Friday in their final regular-season game.

First-half goals from Markel Susaeta and Mark Milligan proved enough to get the job done on Monday, with Iker Guarrotxena netting United's consolation.

While the hosts have now lost seven on the bounce, Macarthur have suffered only one defeat in their past eight matches.

Matt Derbyshire set up both goals for the visitors, his headed knockdown handing Susaeta the chance to finish deftly past Ryan Scott in the 27th minute.

And just four minutes later the Englishman teed up Milligan to rifle home from outside the area.

Guarrotxena's powerful second-half header gave United hope but there was to be no comeback.

Ninth-placed Perth Glory are the only team that could deny Macarthur a top-six finish. They sit six points adrift of Macarthur but have a game in hand.