Zhao Xintong of China and seven-time world champion Ronnie O'Sullivan of England battled to a 4-4 stalemate in the first session of their semifinal match at the World Snooker Championship in Sheffield, England, on Thursday.

The 28-year-old Zhao, playing in his first last-four match at the Crucible Theatre, recorded early breaks of 60 and 62 in the first two frames, en route to claiming a 2-0 lead in the match.

O'Sullivan, 49, responded immediately with three half-century breaks to surge into a 3-2 advantage.

The pair split the next two frames before Zhao put together a run of 86 to level the score at 4-4, with the second session slated to get underway early on Friday.

In the other semifinal contest, home favorite and World No. 1 Judd Trump took a 5-3 lead after eight frames against three-time world champion Mark Williams of Wales.