The dollar index, measuring its strength against a basket of other major currencies, rose to a three-week high just above 80.30. It strengthened past resistance around $1.38 per euro to trade about 0.5 percent stronger just below $1.38.
The yen fell 0.13 percent to 102.48 yen.
Many analysts have been burnt by the dollar's failure to rise in the first quarter of 2014, hit by a combination of the poorer U.S. economic numbers, the reticence of the European Central Bank to ease its own policy further and a flood of money returning to the euro zone's battered southern bond markets.
Some were unwilling to buy the idea that Yellen's comments marked a watershed in that debate.
If the heart of the argument for dollar strength this year is a rise in the return on U.S. Treasuries then Yellen's comments certainly delivered.
The benchmark Treasury yield was trading around 9 basis points higher than a day earlier at 2.77 percent.
The Canadian dollar slid to a 4-1/2 year low of near C$1.13 against its U.S. counterpart, while the Australian dollar fell back below 91 U.S. cents and was last above $0.90.
The Swiss franc also gave up 0.6 percent against the dollar, unmoved by a Swiss National Bank statement and news conference which tweaked its message on inflation but offered no sign of a shift in policy.
Gallo said there was certainly more room for the dollar to gain against its Canadian counterpart and others. It was roughly a third of a percent higher against the Canadian, Australian and New Zealand dollars.
China's yuan also remained a focus, plunging to a one-year low after the People's Bank set a lower guidance for the currency, the second consecutive daily fall of more than 1 percent from the central bank's midpoint.
The yuan has continued to weaken since the bank announced over the weekend it would double the currency's permitted trading range to 2 percent, underlining growing concerns over China's economy and financial sector.
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