Jamieson Greer, President Donald Trump's nominee to be United States Trade Representative, with the rank of Ambassador, appears before the Senate Committee on Finance for his pending confirmation on Capitol Hill in Washington, D.C., Feb. 6. AP-Yonhap

President Donald Trump's nominee for U.S. Trade Representative (USTR) warned Korea and other countries Thursday against taking regulatory measures that would negatively affect American online technology firms, saying that "it won't be tolerated."

USTR nominee Jamieson Greer made the remarks during a Senate confirmation hearing, as Sen. Mike Crapo (R-ID) accused Korea and the European Union of moving to advance measures targeting U.S. firms with special requirements or taxes while exempting their domestic companies and Chinese firms, and asked him if he would "confront" those measures.

Crapo was apparently referring to Seoul's proposed regulations to reinforce oversight over market-dominant online platform operators to promote fair competition. Amid opposition from U.S. business circles, Seoul is pushing for an alternative measure.

"This is an area where the United States is very competitive, and I understand that we will. We are having a domestic conversation about how to regulate digital trade and technology companies, etc. And my view is that is where the conversation should be happening," he said during the hearing at the Senate Committee on Finance.

"We should not be outsourcing our regulation to the European Union or Brazil or anyone else, and they can't discriminate against us, and it won't be tolerated," he added.

The nominee's remarks appeared to signal that if confirmed, he would take steps to fend off foreign regulatory measures that could restrict U.S. online platform businesses.

Commenting on next year's review process for the U.S.-Mexico-Canada Agreement (USMCA), a free trade deal, Greer noted the need to look at the rules of origin to ensure that third countries or "foreign countries of concern" are not "free-riding" on the agreement at the expense of the U.S. and its trading partners.

USTR nominee Jamieson Greer testifies during a Senate Committee on Finance for his pending confirmation on Capitol Hill in Washington, D.C., Feb. 6. AFP-Yonhap

The nominee was apparently alluding to foreign companies that have production facilities in Mexico for exports to the U.S. Hundreds of Korean firms, including Samsung Electronics and LG Electronics, are operating in Mexico.

In his opening remarks, Greer underscored his vision to make America a "country of producers" in line with Trump's push to strengthen America's manufacturing base, while stressing his priority to ensure supply chain resilience.

"First, it is my belief that America should be a country of producers. We are more than just what we consume," he said. "Americans should have the opportunity to work in good-paying jobs producing goods and services they can sell in this market and abroad to earn an honest living."

He pointed out that ensuring supply chain resiliency is "critical" for the U.S.' economic and national security.

"We continue to live in a period of global volatility, unrest, and conflict as foreign adversaries invade other countries, build up their nuclear arsenals, and seek to overtake America's technological edge," he said.

"If the United States does not have a robust manufacturing base and innovation economy, it will have little in the way of hard power to deter conflict and protect Americans."

During the first Trump administration, Greer served as chief of staff to USTR Robert Lighthizer. He previously served in the U.S. Air Force Judge Advocate General's Corps, including a deployment to Iraq.

He earned his bachelor's degree in international studies from Brigham Young University and J.D. from the University of Virginia School of Law. (Yonhap)