BEIJING (AP) — China on Monday criticized President Donald Trump's threat to cut off U.S. trade with countries that deal with North Korea and rejected pressure to do more to halt the North's nuclear development.

Trump issued the threat after North Korea on Sunday exploded a thermonuclear device in its sixth and most powerful nuclear test. The threat was seen as a warning to China, North Korea's main trading partner and only major ally.

A foreign ministry spokesman, Geng Shuang, criticized Trump's stance as unfair to Beijing.

"What is definitely unacceptable to us is that on the one hand we work so hard to peacefully resolve this issue and on the other hand our interests are subject to sanctions and jeopardized," Geng said at a regular news briefing. "This is unfair."

Such an approach would be drastic if applied to China, from which the United States imports goods worth about $40 billion a month.

Trump said it was under consideration "in addition to other options."

Asked whether Beijing would support tougher U.N. sanctions such as cutting off oil supplies to North Korea, Geng didn't mention oil but said whatever happened would depend on discussions among council members. Geng said China, one of five permanent Security Council members with power to veto U.N. actions, would take part in a "responsible and constructive way."

Geng expressed frustration at Australian Prime Minister Malcolm Turnbull's comment that Beijing had a responsibility to influence North Korea due to its status as the North's main trading partner.

"We keep stressing that we cannot solely rely on China to resolve this issue," said Geng. "We need all parties to work in the same direction."