Rising Sun puts heat on Hackett record

Chinese teen sensation Sun Yang Saturday cruised through to the final of the world championships 1500m freestyle as he eyes an assault on Australian Grant Hackett's 10-year-old record.

The host nation are second behind the United States at the top of the swimming medals table in Shanghai on four golds compared with the Americans' haul of nine, but Sun looks a virtual certainty to win Sunday's 1500m final.

The 19-year-old, who clocked 14min 48.13sec to top the timings in the heats, has already won gold in the 800m freestyle and silver in the 400m as he continues his meteoric rise.

"It's an easy race this morning. As for the final, I hope I can do my best and surprise everybody, but nobody knows what will happen," said Sun.

On the last night of pool action on Sunday, Sun is expected to mount a challenge to Hackett's world record time of 14:34.56 set in 2001, after missing out on the mark by less than a second at last year's Asian Games in Guangzhou.

So far just one world record has fallen in Shanghai, to America's Ryan Lochte in the 200m individual medley, after a glut of 43 at the 2009 worlds when swimmers wore the high-tech, polyurethane swimsuits which are now banned.

Also in Saturday's heats, America's Rebecca Soni qualified joint second quickest for the semi-finals of the 50m breaststroke in 30.72sec with Russian Yuliya Efimova as she seeks a third title after winning the 100m and 200m.

But she played down her chances in a strong field including the likes of world record-holder Jessica Hardy of the United States and defending champion Efimova.

"I'm really happy. It's been a great run so far and now it's the fun stuff, the (4x100m medley) relay and 50m," said the Olympic 200m breaststroke champion.

Elsewhere, British world record holder Liam Tancock reached the semi-final of the men's 50m backstroke, qualifying joint 10th fastest in the heats.

"It was nice to get in and post a decent time to put me through to the semi-final, which was the main aim," he said.

Highlights later Saturday, on the penultimate night of action, include Michael Phelps going for his third gold in Shanghai in the 100m butterfly after a mixed championships in which he has twice lost to Lochte.

Phelps, the 14-time Olympic gold-medallist, has struggled to find his peak after long periods neglecting training, although he has two golds including the 4x200m freestyle -- thanks to Lochte's anchor swim -- and the 200m butterfly.

And dope row swimmer Cesar Cielo of Brazil will seek to add a second successive 50m freestyle title to his 50m butterfly gold won earlier in Shanghai.

The reigning world and Olympic 50m freestyle champion escaped a ban on the eve of the competition despite testing positive for a banned diuretic, a ruling which drew an irate response from fellow swimmers.