The USTR report, released last week, said that the Korea deal "coincided with a dramatic increase in our trade deficit" with the South, noting that the total value of US goods exported to South Korea fell by $1.2 billion, while US imports of goods from South Korea grew by more than $13 billion.

The report is seen as a strong indication that the US could seek a renegotiation of the pact.

"The trade balance in goods is not the entire picture in any international economic relationship," Manzullo said in the article.

"The US has always had a trade surplus in services with Korea, hitting another record-high for 2016. When service sector exports are included, the bilateral US-Korea trade deficit drops to $17.5 billion, revealing a more accurate picture of the trade relationship."

He also said that not every product or service was covered by the trade pact as some were already provided duty-free treatment prior to the adoption of the agreement, and some products were excluded or subject to longer phase-out periods before the tariff or trade barrier was eliminated.

"US exports of FTA beneficiary goods increased by 18 percent between 2011 and 2015, while exports of non-beneficiary items decreased by 20 percent. One example of a beneficiary items is beef, a sensitive issue in US-Korea trade relations," Manzullo said.

The trade deal has contributed to a 31-percent growth of US beef exports to Korea over 2015 levels, and as a result, America's share of Korea's imported beef market grew to 42 percent in 2016 from 35 percent, while Australia's share fell from 57 percent to 49 percent, Manzullo said.

"Any effort to alter KORUS will threaten these enhanced market opportunities for US producers," he said.

In addition, according to the Commerce Department, 358,000 US workers owed their jobs to exports to Korea in 2015, an increase of 87,000 jobs since 2009, Manzullo said, adding that the increase was most pronounced for the merchandise export sector, which added 55,000 jobs in the same time period.

"Jobs supported by exports pay, on average, 18 percent more than other jobs. Employees in the 'most trade-intensive industries' earn an average compensation package of salary and benefits of nearly $94,000. These jobs are spread throughout the United States," he said.

"While every agreement can be reviewed every few years to determine if the deal is still accomplishing its original goals, a preliminary assessment shows that the KORUS FTA has benefited both sides and continues to contribute greatly to the strength of the strategic alliance between the US and the Republic of Korea," he said. (Yonhap)