The Communication Workers of America has weighed in against Japan becoming part of the Trans-Pacific Partnership, a major free-trade pact that encompasses 40 percent of the world’s gross domestic product.

In a statement, the CWA said:

Japan’s entry would cause the loss of tens of thousands of U.S. jobs, further damaging an already weak U.S. economy.  Japan is the second largest source of the U.S. trade deficit after China, and given the nation’s experience with other trade agreements, Japan’s entry into the TPP would make this trade deficit even worse.

Japan’s history of currency manipulation would further exacerbate this trade deficit if allowed to continue.  For example, just in the six-month period, from September 2012 to March 2013, the yen has been devalued by 21 percent, making Japanese exports to the U.S. cheaper and imports from the U.S. even more expensive.

Furthermore, Japanese automakers in the U.S. routinely violate global standards on workers’ rights to organize and bargain collectively.

Read the full statement here. CWA is one of the largest and most influential unions. It’s opposition will put pressure on the administration to also oppose Japan. The pact has been controversial on both sides of the Pacific, with Japan only recently deciding to weigh in.