Juan Martin del Potro moved a step closer to winning his first ATP title in almost three years with a straight-sets win over third seed Ivo Karlovic in the Stockholm Open quarter-finals.

Del Potro - runner-up at the Rio Olympics earlier this year - has not won a tournament since the Sydney International in January 2014, but moved to within two matches of ending that wait on Friday.

The 28-year-old won 6-3 6-4 in only 71 minutes against big-serving world number 21 Karlovic, with one break in each set proving decisive.

Wildcard Del Potro will now meet Grigor Dimitrov in a Saturday semi-final.

"I was expecting a tie-break in this match, but I'm happy to get the rest for tomorrow when I play Grigor," the Argentinian said after the victory.

Number two seed Dimitrov had to work much harder to progress by beating Kevin Anderson 7-6 (7-3) 5-7 6-2.

A pair of mini-breaks in the tie-break proved decisive in a first set that went with serve, but the Bulgarian fell apart in the second, throwing away a 5-3 lead as Anderson forced a decider by winning four straight games.

However, Dimitrov composed himself to comfortably take the final set and claimed victory with his first match point after two hours, 18 minutes of action.

The other semi-final will be contested by American Jack Sock and German teenager Alexander Zverev.

Sock won 6-4 6-4 against Gastao Elias, who had conquered top seed Gael Monfils last time out, while Zverev saw off qualifier and compatriot Tobias Kamke 6-3 7-6 (7-5).