The yen weakened slightly Friday but then continued strengthening again as traders doubted Japan's ability to rein in the currency's rally to a 22-month high.
The currency slipped as much as 0.5 percent earlier Friday after Finance Minister Taro Aso spoke of concern about the yen's path, calling for coordination over what he described as disorderly moves in foreign-exchange markets.
"We have to monitor the currency market with a sense of urgency so that speculative moves won't continue — when needed, I'd like to take firm action in line with G-7 and G-20 agreements," Aso, who is also deputy prime minister, said Friday. "Abrupt changes are not desirable and I think it's very important for the exchange rate to be stable."