Ding Junhui's bid to become only the second Asian winner of Snooker's Premier League remained on course with a 5-3 semi-final victory over Judd Trump at Potters on Saturday night.

But to triumph on Sunday he will need to beat nine-times Premier League champion Ronnie O'Sullivan, who had a relatively comfortable 5-2 win over Mark Williams in the night's other last-four clash.

'It's always tough because I have the utmost respect for Mark – he is a top player and you're never safe,' said O'Sullivan. 'I didn't settle quickly and it took me a bit to get my confidence, but in the end I played well.'

In the evening's opening first to five frames semi-final Ding made the best of the early running with a break of 42 after Trump perched a pink on the edge of the middle pocket. A missed red let Trump back in, but he couldn't take full advantage and Ding returned to clear.

The bitty start in front of an enthusiastic Hopton-on-Sea crowd continued with an attritional second, but after more than 29 minutes it was Trump that came out on top as Ding's come-back ended with an over-cut blue.

Trump was first in again for the third but was wasteful in the balls. However, his careless red was matched by Ding's missed black off the spot and the Bristolian returned with 58 to settle down and edge ahead.

Back came Ding, his assured 59 mopping up the fourth before the man from China topped that with an excellent 139 – the second highest of the tournament – to regain the lead.

After a slow start the semi was flowing now and while Ding and Trump both had nibbles in a topsy turvy sixth, it was Trump who fluffed his lines and Ding pinched a potentially defining two-frame lead.

Trump notched 43 before missing a relatively simple cut into the middle pocket – but still saw through frame seven.

However, Ding took his chance in style with some exquisite break-building and a superb 75 to book his place in Sunday night's final – and still harbours hopes of matching the tournament victory of Hong Kong's Marco Fu in 2003.

Next up was Williams and O'Sullivan, who had to make a late dash to the 1,000-seater International Arena for his start after getting a late call.

And it showed as Williams put together two modest breaks to take the first frame to nil.

Ronnie got in with a wonderful long pot in the second before his sloppy black kicked off a bit of to and fro. However, the Rocket visibly settled to take advantage of a Williams slip and get off the mark.

The Rocket was in his stride now; one miss from the Welshman and the nine-times champion pocketed 109 to take a quick-fire lead.

Williams eventually strung enough together in a cagey fourth to level, but from there it was all O'Sullivan. An opening 55 proved enough for him to retake the lead before a break of 84 doubled his advantage.

And in the blink of an eye, Williams' frustration returned O'Sulivan to the table – with the ball in hand, the Rocket racked up 88 to book his extended Potters stay.