Khawaja departs Sydney Thunder in BBL

Usman Khawaja is leaving BBL franchise Sydney Thunder so he can be closer to his family in Brisbane next summer.

Khawaja says seeking a release from his contract with the Thunder was the toughest decision of his cricket career.

Khawaja's wife Rachel is expecting their second child, due in April this year.

The 35-year-old, who was contracted by the Thunder until the end of the next BBL season, says he wants to spend more time in the Queensland capital with his family next summer.

"It's the toughest call I've made as a cricketer because Sydney Thunder ... mean so much to me," Khawaja said in a statement on Friday.

"However, it is for family reasons.

"And while I'm leaving, people who know me realise a big part of my heart will always remain with Thunder.

"I don't want people to think I've cut my ties ... because I'll always care about the club, the players, the entire organisation."

Khawaja's statement didn't specify if he wanted to continue his BBL career with the Brisbane Heat.

Khawaja, an inaugural Sydney Thunder player, is the franchise's leading run-scorer with 1818 runs at a strike rate of almost 130.

Cricket NSW's head of male cricket, Michael Klinger, said the Thunder had tabled a long-term contract extension to Khawaja.

"It's disappointing ... Sydney Thunder and Cricket NSW definitely wanted him to stay and we offered a highly competitive contract," Klinger said in a statement.

"However we appreciate Usman's decision has been made for his family, and we respect and support that."

Khawaja returned to Australia's Test team during the 4-0 Ashes series win against England and departs this weekend for a three-Test tour of Pakistan, the country of his birth.