China has helped build North Korea's ballistic missile program by providing important military equipment and technology, a US expert claimed Wednesday.

In an interview on Fox Business, Gordon Chang, an East Asia security expert, said Chinese President Xi Jinping has been "fueling" the regime in Pyongyang with transfers of "very important" weapons, equipment and technology.

"They're weaponizing the North," he said, citing the ballistic missile program in particular.

The intercontinental ballistic missiles North Korea fired on July 4 and 28 were transported to their launch sites on Chinese mobile launchers, according to Chang, author of "The Coming Collapse of China."

"Those mobile launchers make North Korea a real threat because their missiles can now hide," he said.

Other North Korean missiles launched in August last year and February and May this year also appeared to be variants of China's JL-1 submarine launched missiles, according to the expert.

"That is something the Trump administration needs to talk to the Chinese about," he said.

Trump is set to visit China next month as part of his first trip to Asia since taking office.

His relations with Beijing, according to Chang, are subordinate to his policy on North Korea.

"He will be good to China if he believes China is cooperating with us and he'll be harsh on them if he believes they're not," he said.

Trump's Asia trip will also take him to South Korea on Nov. 7. (Yonhap)