Japanese Prime Minister Shinzo Abe’s recent visit to the U.S., which demonstrated the strengthened Washington-Tokyo alliance, has caused concern here that South Korea may be sidelined from the changing geopolitical dynamics in Northeast Asia.

Members of the parliamentary foreign affairs committee admonished Foreign Minister Yun Byung-se on Monday for what they saw as Seoul’s diplomatic inaction. Many South Koreans are worried that Abe is consolidating Japan’s alliance with the U.S. while refusing to face up to its past history shared with South Korea.

As Yun once noted, however, it might be too simplistic to view relations among South Korea, Japan and the U.S. as a zero-sum game, in which a gain for one side translates into a loss for another. This seemingly unfavorable atmosphere could be turned into an occasion for Seoul to think hard about how to secure and enhance its interests based on cool-headed calculation.

In this regard, Seoul needs to be more active in joining the Trans-Pacific Partnership, an extensive regional trade deal being pushed by U.S. President Barack Obama as a cornerstone of his second-term agenda.

South Korea has remained lukewarm on participating in TPP negotiations while focusing on concluding a bilateral free trade agreement with China. This stance seemed to disappoint the U.S., which last year showed a negative response to Seoul’s wish to become a founding member of the trans-Pacific trade accord. At the time, U.S. officials expressed concern that its belated participation would complicate and prolong negotiations underway among the U.S., Japan and 10 other countries along the Pacific Rim.

For its part, Seoul does not seem particularly frustrated with Washington’s half-hearted reaction. Officials here note South Korea has concluded bilateral free trade deals with most of the countries involved in the TPP talks, saying its exclusion from the launching of the trade bloc would have no significant impact on its economy.

That may not be the case. Over the past years, Japan has lagged behind South Korea in concluding FTAs with major trading partners. But its TPP membership would offset the advantages enjoyed by South Korean exporters to the U.S. and other regional markets. They might even be put under worse conditions than Japanese companies. With major export items of the two countries overlapping, the effect would be felt more acutely.

South Korea also needs to take into account the possibility that its participation will be delayed for a considerable time after the TPP is launched. Its entry should be preceded by specific negotiations with Japan as the two countries have no mutual free trade deal. Nobody can be sure that the process will be easy.

The Obama administration seems to be pushing to secure the TPP as part of its rebalance to Asia policy, which is partly aimed at keeping a resurgent China in check. In a joint news conference following their summit last week, Obama and Abe renewed their commitment to an early conclusion of the deal. Still, the lack of a final accord between the two leaders stood out given their agreement in other areas, showing they have yet to clear domestic obstacles.

It may not be too late for Seoul to reinvigorate efforts to become a founding member of the TPP. It should try to convince the Obama administration that South Korea’s participation from the outset would be in the strategic interest of the U.S. in view of consolidating the Seoul-Washington alliance and enhancing their trilateral cooperation with Tokyo. Keeping South Korea out of the multilateral trade framework will not be helpful for Washington’s effort to reconcile its two key Asian allies.