The top foreign policy adviser to Republican presidential candidate Donald Trump blasted the free trade pact with South Korea again on Monday, calling it a "mistake" that more than doubled American trade deficits with the Asian country.

Sen. Jeff Sessions (R-AL), who oversees Trump's foreign policy team, has expressed deeply negative views of free trade deals, often using the pact with South Korea as an example to make the case the administration of President Barack Obama duped the country into supporting deals that turned out to be bad for the U.S.

"I supported most of the trade deals. I supported the Korean -- when the last big one. I supported the China deal. I think they were now mistakes," Sessions said on MSNBC. "The data came in. It was not anything close to what they promised."

"In Korea, they promised -- when Obama signed it and I voted for it -- that we would increase exports to Korea by $10 billion a year. It was $30 million in increase last year, four years later.

Whereas their imports to us were $15 billion increase. The trade deficit is more than double," the senator said.

Sessions said that the U.S. is a trading nation and he believes in trade, but stressed that the U.S. shouldn't allow its trading partners "to cheat, to manipulate the currency manipulation and other things that take jobs unfairly."

He also said that Trump can show "we've had bad trade deals and how things are not working well."

Trump has also been critical of free trade.

In an economic policy speech early this month, the billionaire real-estate tycoon claimed that the free trade deal with Korea enlarged U.S. trade deficits and cost American jobs. He called the pact, which has been in effect since 2012 and is considered a symbol of the economic alliance between the two countries, "a job-killing deal."

Trump also vowed to pull out of the yet-to-be-ratified, 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 Canada and Mexico agree to a renegotiation.

These negative views have reinforced concern that Trump could seek a renegotiation of the deal with Korea.

Walid Phares, another foreign policy adviser to Trump, said in an interview with Yonhap New Agency in May that Trump wants to go back to "ground zero" with regard to the trade deal.

These claims run counter to the view of the International Trade Commission that the Korea deal has been good for American interests.

In a report late last month, the ITC said that the agreement with Korea is estimated to have improved bilateral merchandise trade balances by $15.8 billion last year. That means that had it not been for the deal, the U.S. trade deficits would have been larger. (Yonhap)