US President Donald Trump is expected to call on Monday for his chief trade adviser to investigate China's intellectual property practices, website Politico has reported, citing an unnamed administration official.

Trump had been expected to order a so-called Section 301 investigation under the 1974 Trade Act earlier this month, but action had been postponed as the White House pressed for China's cooperation in reining in North Korea's nuclear program.

Politico said it was not clear how much detail Trump would provide in his announcement, but administration officials expected US Trade Representative Robert Lighthizer to open a section 301 probe.

Officials at the White House and US Trade Representative's office were not immediately available for comment.

Trump has suggested he would go easier on China if it were more forceful in getting North Korea to rein in its nuclear weapons program.

While China joined in a unanimous UN Security Council decision to tighten economic sanctions on Pyongyang over its long-range missile tests, it is not clear whether Trump thinks Beijing is doing enough.

"We lose hundreds of billions of dollars a year on trade with China. They know how I feel," he told reporters on Thursday. "If China helps us, I feel a lot different toward trade."