Republican presidential nominee Donald Trump on Monday slammed the U.S. free trade agreement with South Korea as a "perfect" example of "broken promises," claiming the deal ended up killed American jobs instead of creating them.

Trump made the remark in a major economic speech in Detroit in an effort to rally support in one of the "rust belt" cities with declining economies, blaming free trade deals for job losses and other economic woes and accusing his Democratic rival, Hillary Clinton, of backing such agreements.

"She supported Bill Clinton's NAFTA, she supported China's entrance into the World Trade Organization, she supported the job-killing trade deal with South Korea, and she supports the Trans-Pacific Partnership," Trump said. "Let's talk about South Korea for a moment, because it so perfectly illustrates the broken promises that have hurt so many American workers."

Trump said President Barack Obama and experts had predicted that the trade deal would increase U.S. exports to South Korea by more than $10 billion, resulting in some 70,000 jobs.

"These pledges all turned out to be false. Instead of creating 70,000 jobs, it has killed nearly 100,000, according to the Economic Policy Institute," Trump said. "Our exports to South Korea haven't increased at all, but their imports to us have surged more than $15 billion -- more than doubling our trade deficit with that country."

Trump has repeatedly criticized the trade pact with South Korea, calling it a "job-killing" deal and even a "disaster." The agreement has been in effect since 2012 and has widely been considered a symbol of the economic alliance between the two countries.

Trump has also denounced other trade deals under his "America first" foreign policy.

The real-estate businessman has vowed to pull out of the 12-nation Trans Pacific Partnership if elected president. He also said he would immediately renegotiate the North American Free Trade Agreement to get a better deal, and withdraw from the deal unless NAFTA partners agree to a renegotiation.

On Monday, he repeated the pledge to renegotiate NAFTA, saying, "If we don't get a better deal, we will walk away." He also argued that the TPP will be "an even bigger disaster for the auto industry."

Trump is expected to seek renegotiation of the Korea trade deal if he's elected to the White House. Though he hasn't directly mentioned such a possibility, aides have long said that he wants to reevaluate or go back to "ground-zero" with regard to free trade agreements.

Attempts to revise or renegotiate the agreement could set off diplomatic tensions. (Yonhap)