SHANGHAI (Reuters) - American Colin Edwards put his Yamaha on pole position for Sunday's Chinese Grand Prix while Spanish MotoGP rookie Jorge Lorenzo gritted his teeth and qualified fourth despite a fractured left ankle.

Tech3 rider Edwards put in a late flying lap of one minute 58.139 seconds to beat former Yamaha works team mate Valentino Rossi by 0.355 and secure the third pole of his career and the Japanese manufacturer's fourth in four races.

Australian world champion Casey Stoner was third fastest for Ducati with Lorenzo, the joint-championship leader with compatriot Dani Pedrosa, qualifying just behind them on the second row.

Lorenzo, winner of the previous race in Portugal and on pole in the last three starts, had looked doubtful for qualifying after being thrown off his bike in Friday practice and taken to hospital.

However he completed 21 laps in Saturday's morning practice.

"The way I felt yesterday, I couldn't even imagine a result like this today," said the Majorcan rider, who celebrates his 21st birthday on Sunday.

Heavy rain is forecast for Sunday at the Shanghai circuit, which could make for an unpredictable race.

Spain's Alvaro Bautista took pole position for the 250cc race on an Aprilia with Britain's Bradley Smith fastest in the 125cc category.

The pole was 17-year-old Smith's third of the season.

"It's great getting pole but with two non-finishes in the opening three races I need to translate that into the race," said the teenager.

(Writing by Alan Baldwin in London, editing by Clare Lovell)