In a statement following the Fed’s latest policy meeting, Yellen cited concerns about the impact on the US economy of recent turmoil in global markets, weakness in China and Europe, and the plunge in crude prices.
Her comments came after the central bank cut its outlook for US growth for this year and painted a picture of the economy that was less upbeat than many had expected.
Crucially it forecast a slower pace of interest rate rises than foreseen in December, when it announced its first hike in almost a decade.
Yellen said policymakers had opted for “a slightly more accommodative path” given “soft” US business investment and weak exports in recent months.
The prospect of rates staying at ultra-low levels for some time boosted US shares, gains that extended into Asian trade.
Hong Kong added 1.2 percent and Shanghai also put on 1.2 percent, while Sydney ended up one percent and Seoul was 0.7 percent higher. Singapore added one percent and Manila rallied almost two percent.
However, Tokyo succumbed to late selling to end 0.2 percent down.
In early European trade London added 0.6 percent, Frankfurt gained 0.7 percent and Paris put on 0.9 percent.
“The Fed’s stance is relatively friendly,” Mitsushige Akino, executive officer at Ichiyoshi Asset Management Co. in Tokyo, told Bloomberg News.
“The difference in the stance between the market and the authorities has shrunk, and we’ve managed to get through an important event without drama.”
– Dollar tumbles -The dollar tumbled to 111.84 yen on Thursday, down from 112.57 yen in New York.
The euro jumped to $1.1249 Thursday from $1.1226 in US trade and well up from the $1.1090 in Tokyo Wednesday.
The dollar plunged against emerging currencies, with the South Korean won up 1.7 percent, the Australian dollar 2.3 percent higher, Indonesia’s rupiah put on 1.4 percent and the Thai baht was 0.6 percent higher.
There were also sharp gains for the New Zealand dollar and Singapore dollar. The oil-dependent Malaysian ringgit rallied 1.3 percent.
On oil markets, US benchmark West Texas Intermediate surged almost six percent Wednesday and Brent more than four percent as the weaker dollar makes the commodity cheaper for clients using other currencies. In afternoon trade Thursday WTI added 2.2 percent and Brent 1.3 percent.
Adding to buying sentiment was news that key producers including Saudi Arabia and Russia will hold a meeting next month to discuss output levels, with hopes they will agree a freeze.
The jump in crude boosted energy firms, with Hong Kong-listed CNOOC up more than five percent and PetroChina 4.4 percent higher.
In Sydney, Rio Tinto gained 2.4 percent and BHP Billiton was also up 2.4 percent.
– Key figures around 0830 GMT -Tokyo – Nikkei 225: DOWN 0.2 percent at 16,936.38 (close)
Shanghai – composite: UP 1.2 percent at 2,904.83 (close)
Hong Kong – Hang Seng: UP 1.2 percent at 20,503.81 (close)
London – FTSE 100: UP 0.6 percent at 6,212.68
Euro/dollar: UP at $1.1249 from $1.1226 on Wednesday
Dollar/yen: DOWN at 111.84 yen from 112.57 yen
New York – Dow: UP: 0.4 percent at 17,325.76 (close) – AFP