The success of Japan and South Korea at inserting language voicing concern over their currencies in a joint statement with the U.S. this week underscores the political heat they face from stiff inflation that is being aggravated by weak exchange rates.

The matter is all the more urgent with Middle East tensions threatening to push up oil prices and accelerate cost pressures that have already exacted a domestic political toll on both governments. For the U.S., the statement was a small price to pay to placate a pair of allies it needs to keep on board with a more strategic goal of containing China.

In the first trilateral finance dialogue since last year's historic three-way leaders summit at Camp David, the U.S., Japan and South Korea agreed on Wednesday to "consult closely" on currency markets, acknowledging "serious concerns" from Tokyo and Seoul over the slumping Japanese yen and South Korean won.