Star swimmer Sun Yang's relationship with his long-time mentor remains tense.

After drawing unwanted headlines in February for breaking team rules, China's double Olympic champion still hasn't apologized to coach Zhu Zhigen after threatening to replace him during a quarrel earlier that month.

"I required him to do a deep introspection (for his disrespectful behavior). But he hasn't done it yet, nor said sorry to me," Zhu was quoted as saying in a Xinhua report on Wednesday.

In a bid to end the impasse, Shang Xiutang, director of the national swimming administrative center, visited the Zhejiang College of Sports last week to talk with both sides.

"My visit was to try to find out what happened between them. They both showed positive attitudes to reach an agreement and leave all the unhappy things behind. But Sun hasn't apologized to Zhu in person," Shang told Shanghai-based Oriental Morning Post on Thursday.

Concerned that too many commercial activities were taking a toll on Sun's training, Zhu also voiced his disapproval at the 21-year-old star's budding romance with a flight attendant, claiming dating at such a young age would hamper his performance.

Zhu tried to persuade Sun to spend more time in the pool instead of missing practice sessions to date his girlfriend, but met fierce resistance from Sun, who asked a college official for a new coach.

However, Zhu and Shang have both suggested the relationship will continue.

"No, I never said that," Zhu responded to the query, "Have you already decided to split with Sun?" from Xinhua.

Shang also believes the duo's long-term bond won't be ended by an impulsive quarrel.

"We've been stressing the importance of communication to them. They have worked together for 10 years and that emotional bond won't be ruined overnight. I think the ice will melt once Sun and Zhu talk to each other and work together at the pool."

According to the college, Sun will resume training on Friday after staying away from practice for almost two months due to endorsement activities and other assignments.

With one month to go before the national swimming championships, which begin on April 1, time is short for Sun to regain his form and qualify for this year's National Games and FINA World Championships.

"The priority now is to urge Sun to recover his shape and stroke as quickly as possible," Shang said.

Meanwhile, the official also denied a rumor that Sun's girlfriend would be hired as his agent.

"It's impossible. The governing body has clear rules that all athletes affiliated with the State-run system are not allowed to sign personal agents. The swimming center will take care of all of Sun's commercial affairs."