BEIJING (AP) -- China's trade with North Korea has risen despite Beijing's promise to enforce U.N. sanctions over its nuclear program, but Chinese purchases of most North Korean exports have fallen.

Customs data show total Chinese-North Korean trade in the first five months of this year rose 15 percent from a year earlier. Exports of Chinese oil to the North rose, while China's purchases of iron ore increased.

Trump wants Beijing to use its status as North Korea's only major ally and source of oil and export markets to pressure Pyongyang to renounce nuclear development. But Chinese leaders are reluctant to press the North too hard for fear its government might collapse.

"Unless North Korea starts a war against China or some other country, China will not cut off all trade," said Shi Yinhong, an international relations specialist at People's University in Beijing.

"Some (economic) activities are not for making money but for political concerns, so the people in Pyongyang will want to listen to us sometimes when we talk," said Shi. "The United States does that too."

Trump on Wednesday cited a Chinese Customs agency statement that Chinese-North Korean trade rose 36.8 percent from a year earlier in the first quarter of the year.

That appeared to be at odds with Chinese data that showed a rise of just 7.4 percent. But the Customs agency said Thursday in an emailed response to questions the change was bigger due to a revision in last year's figures that was not published. It gave no other details.

Following the North's fifth nuclear test in November in defiance of U.N. demands, Beijing announced in February it was suspending imports of North Korean coal, a key revenue source for the Pyongyang.

As a result, Chinese purchases of North Korean coal are off 45 percent this year, according to a South Korean industry group, the Korea International Trade Association.

At the same time, Chinese purchases of North Korean iron ore, a key export for the mineral-rich North, rose 34 percent over a year earlier, according to KITA.

Chinese oil sales to the North rose 18 percent in the first five months of the year to $35 million, according to KITA.

Other top Chinese exports to North Korea included telephone equipment, textiles, soybean oil and vehicles, it said.

Total trade for the first five months of the year was just over 14 billion yuan ($2.1 billion), a tiny sum for China, the world's biggest trader. But the relationship with North Korea, which shares a border with China, is politically significant.

In a sign of growing frustration, Beijing agreed for the first time in March 2016 to enforce U.N. Security Council sanctions following Pyongyang's test of a missile possibly capable of carrying a nuclear warhead.

China banned coal imports the following month but allowed some purchases for civilian use. That reflected Beijing's strategy of trying to push the North's leadership to comply without destabilizing its economy.

Without coal sales, trade growth is driven instead by rising Chinese exports to the North, leaving Pyongyang with a widening trade deficit. In May, three-quarters of total trade consisted of Chinese exports to the North.

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AP Business Writer Youkyung Lee in Seoul and researcher Fu Ting in Beijing contributed.