NOTTINGHAM, England (AFP) - Reigning champion Ivo Karlovic needed three sets to reach the semi-finals of the Nottingham Open here Thursday.

The tall Croatian was given a tough test by Italian Andreas Seppi before winning 6-3, 3-6, 6-4.

In the second set seventh seed Seppi became the first player this tournament to break Karlovic's powerful serve after the title-holder had had things pretty much his own way in the opening stages.

But Seppi played his way back into the match with some fine passing shots before Karlovic's serve again clicked into gear.

Both players held serve for most of the final set until Seppi, at 4-5 down, let slip a 40-15 lead with Karlovic wrapping up proceedings on his second match point with a backhand volley.

Karlovic will face Gael Monfils in the semi-finals after the French Open semi-finalist defeated American qualifier Vince Spadea in straight sets.

Monfils, who beat Karlovic on clay at Monte Carlo two months, played down the prospect of having to deal with the Croat's huge serve.

"For sure it will be tough but I'm not thinking about it for now."

Karlovic admitted a stiff breeze had reduced the effectiveness of his serve.

"It was windy today and I was struggling with my serve, especially in the second set, so I was not happy with that but I found my serve again in the third set and managed to pull through."

Spanish third seed Fernando Verdasco needed three sets to beat Gilles Simon while Karlovic's fellow Croat Marin Cilic became the last man into the semis with a convincing 6-1, 6-2 win over Thomas Johansson.