The dollar strengthened in Asian trade on Friday, pinning the yen near a four-decade low as a peace deal between the U.S. and Iran hung in the balance and traders speculated further intervention may be needed to arrest a slide in the Japanese currency. The Japanese currency reversed earlier strength to trade flat against the U.S. dollar at 161.455 yen, grinding closer to its weakest level in two years, though public holidays in China, Hong Kong and Taiwan and an impending one in the U.S. kept liquidity thin.