President George W. Bush's former trade representative is warning that Congress needs to reassert itself on trade policy before President Trump has a "crack-up" on trade.

Robert Zoellick, who was Bush's U.S. trade representative, warned in a Wall Street Journal op-ed that Trump's threat to leave the U.S.-Korea Free Trade Agreement makes no sense, as it gives China more power in the region.

"Mr. Trump's impulses are strategically incoherent," Zoellick wrote. "China has been squeezing Korean companies because Seoul has been installing missile defenses against North Korean rockets."

"When Mr. Trump seeks to cut off South Korea's trade with the U.S., Seoul's logical course is to accommodate Beijing to protect ties with its largest trading partner," he added.

Zoellick also predicted that Trump would eventually blame existing trade deals for the U.S. trade deficit. But he said abandoning these agreements would only end up hurting U.S. companies.

"Mr. Trump appears oblivious to these realities," he wrote. "His real aim may be to forge a domestic political realignment around matters such as trade protectionism, hostility to immigration and walling off Mexico."

"As he is unable to achieve simple solutions in North Korea, Afghanistan and the Middle East — and as his frustrations build with Congress and investigations — the danger is that he will lash out," he added.

"Congress can no longer wait for Mr. Trump to speak and act sensibly," Zoellick wrote. "It needs to assert its constitutional powers over trade to stop this president's destruction."