Venus Williams reached her first singles final of the season at the Luxembourg Open after outlasting Andrea Petkovic in a titanic semi-final.

German Petkovic, playing in her first semi-final of the year after serious injury problems, edged the opening set but Williams battled back to win 5-7 6-4 6-4 in two hours and 38 minutes.

In the final, Williams, who continues to battle the effects of Sjogren's Syndrome, will meet Romania's Monica Niculescu, who was a comfortable 6-1 6-3 winner over Daniela Hantuchova.