(Adds Li quotes)
LONDON, July 2 (Reuters) - Last year's runner-up Agnieszka Radwanska, the highest ranked player left in the women's draw, moved closer to reaching successive Wimbledon finals after outlasting China's Li Na 7-6(5) 4-6 6-2 in an epic last-eight duel on Tuesday.
The Polish fourth seed, seeking her first grand slam title after losing in three sets to Serena Williams 12 months ago, set up a semi-final showdown with German Sabine Lisicki having staved off a Li fightback, the distraction of two rain interruptions and then squandering seven match points.
"She was playing unbelievable tennis I had two tough matches before so I was happy to go through to the semi-finals," a relieved Radwanska told the BBC.
"It was just too much tennis in the last few days that's why I was struggling with my legs."
Former French Open champion Li wasted chances to take the opening set and after a short rain break, the sixth seed hit back to take the second from 4-2 down as her aggressive strokes to the corners of the court, combined with frequent net approaches, began to penetrate.
But Radwanska, who had her right thigh heavily strapped up before the start of the decider, regrouped under the now-closed roof following a second rain delay.
She secured a double break but spurned two match points at 5-1 up and another five in the next game. With nerves frayed, she finally sealed victory when the never-say-die Li, losing in a Wimbledon quarter-final for the third time, went long.
Li was left to pick out the positives of her run to the quarter-finals after a disappointing claycourt season.
"Before I didn't think I could come to the net like I did so many times," she said. "I'm really proud of myself.
"So at least now we have a job to do, me and (coach) Carlos (Rodriguez). We know what we should do for the next step."
Top seed and five-times champion Williams was beaten by Lisicki in the fourth round on Monday, following chief rivals Victoria Azarenka and Maria Sharapova out of the tournament.
Radwanska and Lisicki have met on two occasions with a victory apiece - both on a hard court. The Pole won last year in Dubai with Lisicki's success coming a year before in the United States. (Editing by Ed Osmond)