Positive signs from the US economy have failed to boost the greenback, while tensions in Ukraine are driving traders to the yen.
The yen rose to a two-week high against the dollar on Monday after a survey showing China's manufacturing activity contracted.
The dollar inched up from a three-week low on Friday, on expectations of a robust U.S. jobs number, after a weak growth report earlier this week.
All the economic evidence shows that a currency union between the U.K. and an independent Scotland poses "huge long-term risks" says Danny Alexander, chief secretary to the U.K. Treasury.
The euro trod water in early European trade on Wednesday with all eyes on euro zone inflation numbers due later.
Neil Mellor, senior currency strategist at BNY Mellon, says sterling's strength is due to dollar weakness rather than strong data from the U.K.
The euro traded at multi-week highs against the yen early on Tuesday and held firm against the dollar after a strong performance overnight.
The euro rose to a two-week high against the dollar on Monday, supported by expectations inflation in the euro zone will tick up.
Key U.S. data culminating in Friday's closely-watched jobs report and the Fed's target measure of inflation a day earlier may offer some sustenance to a directionless dollar, CNBC's latest market survey showed.
The dollar struggled against the yen and Swiss Franc as rising tensions in Ukraine offset optimism about U.S. economic growth.
The euro struggled to make headway on Thursday amid caution before a speech by ECB President Mario Draghi.
The US dollar was weakened by falling equity prices, Treasury yields, and a slower-than-expected expansion in the US manufacturing sector.
The European Central Bank's Mario Draghi made clear the euro's strength is a possible trigger to ease monetary policy.
A record Japanese trade deficit in the fiscal year fueled the dollar's rise against the yen, but tensions in Ukraine were likely to limit losses.
The dollar fell against a basket of currencies on Thursday after Federal Reserve chief Janet Yellen reiterated an accommodative monetary policy stance.
The yen fell on Wednesday, hit by comments by Japan's finance minister that traders took as a sign of a weaker yen.
The yen fell against the dollar and the euro on Wednesday, on pension fund comments by Japan's finance minister.
The euro fell after the European Central Bank said it will be forced to ease further if the currency keeps going up.
The dollar lost 2.5 percent against the yen since last Friday, on guidance that the Federal Reserve will not soon raise base interest rates.
The dollar hit a three-week low on Thursday after minutes from the Federal Reserve's March meeting disappointed dollar bulls.