The Nikkei share average ended the day down 0.15% at 21,533.48.

Markets are bracing for Powell's comments, in two days of  testimony before the U.S. Congress starting later on Wednesday, in which he may support or confound expectations for U.S. policy easing.

Global equities had advanced earlier this month on the prospect of the Fed easing monetary policy. But the markets have lost some momentum recently as the prospect of aggressive easing has faded after a stronger-than-expected U.S. jobs report.

"Investors are nervous as they wait to find out from Powell's comments on whether the Fed will continue cutting rates or not," said Yutaka Miura, a senior technical analyst at Mizuho Securities.

Machinery shares languished after Japan Machine Tool Builders' Association said on Tuesday that June orders for machine tools tumbled 38% to 98.8 billion yen ($907.25 million), falling for the ninth consecutive month. Fanuc Corp slipped 2.1% and Yaskawa Electric dropped 1.5%, while Keyence Corp shed 0.7%.

Chiba Bank rallied 3.8% after the lender and Bank Of Yokohama said they were considering a business tie-up.

Concordia Financial Group, Bank of Yokohama's parent company, gained 1.2%.

Japan Post Insurance Co lost 5.1% following reports that it had double charged life insurance premiums to its customers.

Yoshinoya Holdings, which operates beef bowl fast food restaurants, surged 8.8% after it posted a net profit of 1.097 billion yen in the March-May period, compared with a net loss of 388 million yen in the previous year.

The broader Topix fell 0.23% to 1,571.32.

Declining shares outnumbered gainers 1,297 to 764