The dollar index pulled back from three-week lows on Wednesday, as the soaring cable retreated off its highs. Sterling surged after British Prime Minister Theresa May called an early general election ahead of Brexit negotiations.

The pound climbed to its highest in more than six months after May said the election would "secure the strong and stable leadership" position needed for talks with the European Union about terms for the looming exit.

The dollar index, which tracks the greenback against a basket of six rival currencies, edged up 0.1 percent to 99.633, pulling away from its overnight low of 99.465, its deepest trough since March 28.

GBP/USD slipped 0.2 percent on the day to 1.2820 after rising as high as 1.2908 on Tuesday, its highest since early October, as forex investors scurried to cover short positions.

USD/JPY inched up 0.1 percent to 108.58, as the EUR/USD edged down slightly to 1.0719 after riding sterling's coat-tails to three-week highs overnight.

French opinion polls show far-right leader Marine Le Pen and centrist Emmanuel Macron qualifying next Sunday for the May 7 run-off, but the gap with conservative Francois Fillon and far-leftist Jean-Luc Melenchon has been tightening.