The yen may strengthen to 90 per dollar within six months of Donald Trump's election, former Japanese top currency official Eisuke Sakakibara said.

"Trump's 'America first' stance means weak dollar policies," the 75-year-old professor, dubbed "Mr. Yen" for his ability to influence the exchange rate in the 1990s, said Thursday. "Gradual dollar weakness and yen strength are going to continue."

Sakakibara, who accurately predicted the currency's advance this year from near 120 per dollar to beyond 100 for the first time since 2013, said the yen's decline to a three-month low followed Trump's toned-down rhetoric rather than a change in trends. The yen swung to a 0.5 percent loss against the dollar Wednesday from a surge of as much as 3.9 percent, the most since June's Brexit referendum result, after a conciliatory victory speech.