Tathiana Garbin and Flavia Pennetta gave defending champions Italy a 2-0 lead over world-group debutantes China in their Fed Cup quarter-final on Saturday.

Garbin had a much harder time than expected beating China's Sun Tiantian 6-4 2-6 6-3 in two hours 38 minutes in the opening singles rubber.

Pennetta lost her first set against Peng Shuai to love and was down 3-5 in the second before fighting back with a huge surge in vigour and technique, saving matchpoints at 4-5.

The Italian went 3-0 up in the third before Peng, struggling with a hamstring injury, retired, giving Pennetta a 0-6 7-5 3-0 win.

"This is the Italy of miracles," Italian captain Corrado Barazzutti said.

The responsibility of defending the title at home seemed to weigh on Garbin, ranked 23rd in the world, and her first two sets were riddled with unforced errors and double faults.

Sun, Olympic doubles gold medallist and ranked 91st in the world at singles, appeared to have a chance of victory.

In the fifth game of the third set Sun had seven chances to break Garbin's serve but the Italian contested each point fiercely to finally win the game and go on to take the set.

"It was a tough game, especially emotionally," Garbin said. "From a technical point of view I'm not satisfied with the way I played but what counts is winning and I gave it my heart. I hope I play better tomorrow."

China must now decide whether Peng will be fit to play on Sunday in the reverse singles and in the doubles with Sun, against Mara Santangelo and Roberta Vinci.

Italy's quartet are all ranked inside the world's top 51 and comfortable on Castellaneta Marina's slow clay courts.

China are missing two of their best players -- world number 17 Li Na and number 33 Zheng Jie -- who stayed home because of ankle injuries, team captain Zhang Qi said on Thursday.

Italy were surprise winners of the competition last year, eliminating France and Spain before beating Belgium in the final.