* All of Topix's 33 subsectors in positive territory
* Nikkei posts biggest daily gain in 2-1/2 months
* Exporters, banks soar
* Fast Retailing falls on weak same-store sales at Uniqlo
By Ayai Tomisawa
TOKYO, June 5 (Reuters) - Japan's Nikkei rebounded sharply on Wednesday morning thanks to a rally in U.S. stocks after U.S. Federal Reserve Chairman Jerome Powell signalled a possible rate cut in a boost to riskier assets.
The Nikkei share average rose 1.9% to 20,785.71 in midmorning trade, posting the biggest daily percentage gain since March 26.
All of the Topix's 33 subsectors were in positive territory, with the broader Topix also jumping 1.8% to 1,526.26.
Powell said the central bank would act "as appropriate" to address trade war risks a day after St. Louis Fed chief James Bullard said a rate cut may be warranted soon. Powell said the Fed was "closely monitoring the implications" of a trade dispute that has disrupted global markets.
Analysts said that investors are buying back recently battered stocks such as exporters and financial firms, though they caution developments in the trade war will have the ultimate say in future price moves.
"The market knows that even if the Fed cuts rates, global trade tensions won't be resolved easily," said Yutaka Miura, a senior technical analyst at Mizuho Securities, adding that the Fed's message was positive for investors.
Machinery makers and automakers regained some lost ground, with Fanuc Corp up 3.2%, Yaskawa Electric Corp jumping 4.7%, Advantest Corp rising 3.8% and Toyota Motor Corp advancing 2.3%.
Banks and insurers, which hunt for higher yielding products such as foreign bonds, also attracted buyers. Mitsubishi UFJ Financial Group rose 2.2% and Dai-ichi Life Holdings rallied 3.1%.
SoftBank Group Corp jumped 2.8% after it said on Tuesday it expects to book around 1.2 trillion yen ($11.12 billion) in pre-tax profit on the sale of shares in China's Alibaba Group Holding Ltd.
Fast Retailing underperformed the market, falling 1% after the company said that its same-store sales at its Uniqlo clothing outlets in Japan fell 1.8% in may on the year.
Editing by Shri Navaratnam