The benchmark Nikkei 225 index lost 0.41 percent, or 84.18 points, to 20,620.19, while the broader Topix index was down 0.44 percent, or 6.65 points, at 1,505.21.

The United States and China imposing new tariffs on each other's exports on Sunday "overturned" last week's optimism on the trade talks, Masayuki Kubota, chief strategist at Rakuten Securities, said in a note.

"Fears of a global economic slowdown due to tit-for-tat sanctions are likely to continue for a while."

Washington moved ahead Sunday with new tariffs on Chinese imports as it stepped up a high-pressure campaign aimed at coercing Beijing to sign a new trade deal.

The additional tariffs affected a portion of the $300 billion in goods from the Asian giant that so far had been spared.

Beijing said it will retaliate by targeting $75 billion in US goods, beginning in part on September 1.

The dollar slipped to 106.20 yen in Asian afternoon trade from 106.26 yen in New York late Friday.

In Tokyo, some China-linked shares were lower, with industrial robot maker Fanuc down 0.46 percent at 18,370 yen and construction machinery giant Komatsu trading down 0.17 percent 2,253 yen.

Sony edged down 0.09 percent to 6,036 yen as Toyota lost 0.11 percent to 6,952 yen, but Nintendo rose 0.22 percent to 40,380 yen.