Tensions have continued to rise since North Korea carried out its sixth nuclear test on Sept. 3, prompting a new round of U.N. sanctions.
Wang told Japan Foreign Minister Taro Kono on the sidelines of a United Nations meeting in New York that the situation on the Korean Peninsula was getting increasingly serious and all sides needed to remain calm.
"If the Japanese side only talks about sanctions and does not bring up talks, or even goes against talks, it will be seen as contravening Security Council resolutions," the ministry cited Wang as saying.
China hoped that Japan talked and acted cautiously and played a constructive role on the nuclear issue, he said.
Beijing has repeatedly expressed concern about the rise of tensions over North Korea and, while it too has signed up for the increasingly tough UN sanctions, it has also urged a return to talks and for all parties to exercise restraint.
On Friday, Russia urged "hot heads" to calm down as the United States admitted it felt "challenged" by North Korea's warning that it could test a hydrogen bomb over the Pacific.
President Donald Trump called North Korean leader Kim Jong Un a "madman" on Friday, a day after Kim dubbed him a "mentally deranged U.S. dotard" who would face the "highest level of hard-line countermeasure in history" in retaliation for Trump saying the U.S. would "totally destroy" North Korea if it threatened the United States or its allies.