The 26-year-old Shandong midfielder spent Thursday at the London club before heading off to the Asian Games in Qatar, where he will be one of two over-age players in China's under-23 squad.
Zheng helped Shandong to the Chinese Super League (CSL) and Chinese FA Cup double last season before winning his second CSL Player of the Year title. He was named China captain in October.
"It's great our player can play overseas, a kind of honour for both himself and the club," Han told the club's official Web site.
"But it isn't the time for the two clubs to talk about a transfer contract or other details. So far we have not made any contact."
Zheng was banned after attacking an official during an AFC Champions League match last November and it was his tackle that broke French striker Djibril Cisse's leg in a friendly before the World Cup.
Charlton, who are bottom of the Premier League, sacked manager Ian Dowie earlier this month with Les Reed taking over as head coach.