(Bloomberg) -- US Treasury Secretary Janet Yellen said intervention in foreign-exchange markets should be rare, when asked for her reaction to any potential move by Japan to address the slide in the yen against the dollar.

“Adjustments of exchange rates in markets is part of what enables countries to have different policies,” as reflected in the thinking of Group of Seven nations, Yellen said Thursday in a livestreamed interview with Reuters. For “large countries with market-determined exchange rates,” intervention should occur only in rare circumstances, she said.

“We would hope that would be rare, and expect that such intervention would occur only rarely, only with excessive volatility, and they would consult in advance,” Yellen said.

Japanese authorities have warned that they retain the right to intervene in the market as they monitor a tumble in the yen that’s taken it to the weakest in decades against the dollar. The yen weakened beyond 155 per dollar on Wednesday, fueling risk that the key level may prompt Japan to step into the market.

Yellen declined to comment on the appropriate value of the yen.

--With assistance from Reade Pickert.

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