Reuters GraphicsThe dollar has risen 9% this year, as the Federal Reserve has jacked up interest rates to combat inflation at 40-year highs.
As other central banks, from the Bank of England, to the European Central Bank, and the Reserve Bank of Australia, have raised their own rates, dollar bulls have run out of puff.
The close relationship between Japanese monetary policy and U.S. Treasuries adds another twist to the story.
It all boils down to whether Japanese investors have hedged their Treasury exposure or not, he said.
But the stress is on "at the margin", not least because of the sheer size of Japanese investors' holdings of U.S. debt, analysts said.