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The yen’s surge prompted the Group of Seven major industrialized nations to work together to weaken the Japanese currency. Officials feared that the fast rising yen would exacerbate the economic impact of the disaster.

That coordinated intervention in international currency markets was the first by the G-7 countries since the fall of 2000, when the G-7 intervened to bolster the euro.

But the yen’s resurgence after the effects of G7 action dissipated had recently triggered speculation in financial markets that Japan might once again intervene — this time alone — by selling the yen. As the yen dipped to the low 77s Thursday morning, Noda made his announcement that Tokyo had decided to act.

Japan’s move followed the Switzerland central bank’s efforts Wednesday to weaken its currency. It described the franc as “massively overvalued” and issued a strongly worded statement that the country’s economic outlook had deteriorated because of exchange rates.

While it did not directly intervene in foreign exchange markets, the Swiss National bank lowered interest rates and said it would significantly bolster liquidity in the Swiss franc money market.

Lowering interest rates can help reduce a currency’s value against other currencies by lessening demand for investments and assets in that currency.

Switzerland’s currency, along with gold and the yen, has risen sharply because it’s considered a safe haven from the debt and economic woes in the U.S. and Europe.

While Thursday’s intervention by Japan brought some immediate relief, it is unlikely to change longer-term currency trends, said Junko Nishioka, chief economist at RBS Securities Japan.

“As long as concerns for the downside risks in the U.S. economy and expectations for the Fed’s further easing measure persist, it is hard to expect the (dollar-yen) to return to high enough levels to alleviate the negative pressure on exporters’ earnings,” Nishioka said in a research note.