The United States and the European Union will respond on Monday with a ``serious series of steps'' against Russia if a referendum in Ukraine's Crimea region goes ahead on Sunday, U.S. Secretary of State John Kerry said at a congressional hearing.
Fears that this crisis could intensify led traders to shift into the Japanese yen and Swiss franc, which are seen as safe haven currencies in times of geopolitical tension.
The greenback was down 0.7 percent against the yen at 102.04 yen after touching a one-week low of 102.02 according to Reuters data.
The dollar was about 0.2 percent lower near 0.87 Swiss franc after hitting near 2-1/2-year low close to 0.87 franc earlier.
The euro trimmed its earlier gain versus the dollar, last down 0.40 percent under $1.39, after reaching almost $1.40 in European trading. Dealers attributed the loss of altitude to dovish comments made by European Central Bank chief Mario Draghi, who said the bank "stands ready to take further decisive action if needed" on monetary policy.
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