Globally the dollar's sharp rally following U.S. strikes on Iran is reassuring investors the currency still functions as a global safe-haven, with the greenback reclaiming its traditional crisis-era role as geopolitical tensions flare in the Middle East, Reuters reported.

The U.S. dollar appreciated across the board, with the dollar index rising nearly 1%, its best day in seven months.

"Today is, I would say, a classic risk-off day from a U.S. dollar perspective," Eric Theoret, FX strategist at Scotiabank, said.