The Nikkei 225 index rose 0.03 percent, or 7.11 points, to 21,124.00, but the broader Topix index was down 0.45 percent, or 6.97 points, at 1,539.74.

Some blue-chip shares, led by Sony, SoftBank and Uniqlo casual wear operator Fast Retailing, gained ground, offsetting declines in chip-related shares, said Shinichi Yamamoto, broker at Okasan Securities in Tokyo.

"But players were largely on the sidelines ahead of the FOMC (Federal Open Market Commitee) starting on Tuesday," Yamamoto told AFP.

Tsuyoshi Nomaguchi, strategist at Daiwa Securities, said: "If the Fed's view on the economy is hawkish enough to remove market expectations of a rate cut, that would send stocks prices down."

Investors were also watching the US Trade Representative's public hearings on President Donald Trump's plans to impose fresh tariffs on Chinese-made goods, which will start on Wednesday.

"It's worth watching if there is any impact from the US-China trade war on the Japanese trade statistics due on Wednesday," Nomaguchi said.

The dollar fetched 108.59 yen in Asian afternoon trade, against 108.55 yen in New York on Friday.

The Bank of Japan's two-day meeting through Thursday will be monitored as it may affect the dollar-yen rate, analysts said.

In Tokyo, SoftBank jumped 1.84 percent to 10,190 yen while Fast Retailing rose 1.31 percent to 66,930, with Sony up 2.49 percent at 5,635 yen.

Chip-linked shares were lower after the US chip sector declined, with chip-testing equipment maker Advantest dropping 2.91 percent to 2,529 yen and chip-making equipment manufacturer Tokyo Electron diving 2.49 percent to 14,265 yen.