The call comes at a time when Washington and its European allies are ramping up supplies of missiles and tanks to Ukrainian forces in a counter-offensive to retake Russian-occupied territories.
Mr. Li Hui said Russian and Ukrainian officials remained open to peace talks, but he gave no indication that that was imminent.
"China believes that if we really want to end war, save lives and realize peace, it is important that we stop sending weapons to the battlefield, otherwise tensions will only escalate," Li Hui told reporters.
China is a large country with good relations with both Russia and Ukraine and leverages to be one of the largest export markets for both. The decision to send an envoy of Chinese President Xi Jinping was welcomed by the Ukrainian government.
China presented a proposed peace plan in February, but Ukraine and its allies insist President Vladimir Putin must first withdraw Russian troops from Ukraine.
"China's goal is to promote peace talks and end hostilities," said Li Hui, a former Chinese ambassador to Moscow.
Mr. Li repeated Beijing's call to respect "the territorial integrity of all countries". "China supports a balanced and legitimate way to address security concerns," he said.
Mai Anh (according to AP)