The British leader's comments, made while she was en route to Japan, were in response to North Korea's launch of a ballistic missile over Japan yesterday.
The missile launch, which was met with wide condemnation, came less than a month after the UN Security Council imposed its toughest-yet sanctions on the North.
May told reporters on her plane that "we see China as being the key" in the effort to bring pressure on North Korea, according to the British newspaper The Guardian.
"We also noted that some countries stabbed in the others' back while shaking hands with them," Hua said at a regular briefing with reporters.
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"Those countries just sit back and leave others to find a way out. We don't think that is an appropriate attitude of a responsible country," Hua said.
May arrived today in Japan for a three-day visit that is expected to focus on Brexit, trade and security.
During their dinner, May and Abe discussed North Korea's missile launch and agreed to cooperate in urging China to step up pressure on the North, according to Japan's Foreign Ministry.
May's official meetings with Abe and other Japanese officials are scheduled for tomorrow in Tokyo.
It is May's first visit to Japan since becoming prime minister in July 2016.
A delegation of British business leaders is accompanying May. A statement from her office said the delegation would showcase "the shared confidence in the UK-Japan economic relationship as we leave the EU, and the potential for future growth."