The conclusion of the Trans-Pacific Partnership agreement offers a major boost to the United States-Japan bilateral relationship and the promise of closer economic integration. It was agreed Monday after a marathon negotiating session in Atlanta.

But while the mood in official Japan is one of celebration, American experts warn TPP is far from certain to be ratified by the U.S. Congress anytime soon — given that it is becoming a campaign issue among congressional representatives and U.S. presidential candidates.

"In a strategic sense, (the agreement) is huge. TPP establishes the U.S. and Japan as the rule makers when it comes to trans-Pacific trade," said Paul Sracic, a politics and international relations professor at Youngstown State University in Ohio, and an expert on the TPP negotiations.