Del Potro needed 76 minutes to get through his first set with Gonzalez, and finally beat the Chilean on his fourth try.

Gonzalez was playing his first event since resting his knees for a month after a poor Wimbledon.

'We both came from the winter at home in South America,' said Argentine Del Potro. 'Conditions were really hot, it was tough in the heat and humidity,

'I was tired after the end of the first set, so was Fernando,' added Del Potro, who had a rest day Friday when intended opponent Robin Soderling withdrew from their quarter-final injured.

'Fernando's a great player and we are friends,' he said.

'I won only by a couple of service breaks and some good serving. I will need to lift my level a lot in the final.'

Del Potro now has the chance to defend one of the four titles he won last summer during a 23-match win streak in July and August.

The Argentine last lifted a trophy in Auckland in early January and now stands 37-10 in 2009.