Roger Federer of Switzerland returns a ball to Stefanos Tsitsipas of Greece during their semifinal match at the Swiss Indoors tennis tournament at the St Jakobshalle in Basel, Switzerland. Picture: Alexandra Wey/Keystone via AP/African News Agency (ANA)

Top seed Roger Federer dispatched Greek third seed Stefanos Tsitsipas 6-4 6-4 in the semi-finals of the Swiss Indoors championships in Basel on Saturday for his 50th win of the season.

It was a record 16th time that Federer had won 50 ATP tour games in a season and he has yet to drop a set at this year's Basel tournament, where he has now won 23 consecutive matches over the years.

The 38-year-old will be looking to win his 10th title in his hometown when he faces unseeded Australian Alex de Minaur in Sunday's final - the 157th tour-level final of his career.

The Swiss former world number one did not drop serve - with high win percentages on his first (80%) and second serve (85%) - and he broke the 21-year-old Tsitsipas twice in the 78-minute contest.

Federer, who had 28 winners, was also a constant threat when he approached the net, winning nine of 10 net points in the opening set alone.

Earlier, De Minaur beat big-serving American Reilly Opelka 7-6(2) 6-7(4) 7-6(3) in the first semi-final, where break points were in short supply.

Both players dropped serve only once in a match that lasted more than two-and-a-half hours.

Despite Opelka firing 26 aces to De Minaur's 14, it was the 20-year-old Australian who prevailed in the tiebreaks to advance to his sixth ATP tour final and his fourth of the year, having already won titles in Sydney, Atlanta and Zhuhai.