The benchmark Nikkei 225 index was down 0.38 percent or 79.51 points at 20,624.86 in early trade, while the broader Topix index was down 0.28 percent or 4.20 points at 1,507.66.

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

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

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 15 percent tariffs, affecting a portion of the $300 billion in goods from the Asian giant that so far has been spared, took effect.

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

The dollar slipped to 106.19 yen in early Asian trade from 106.26 yen in New York late Friday.

In Tokyo, some China-linked shares were lower, with construction machinery maker Komatsu trading down 0.48 percent 2.246 yen and industrial robot maker Fanuc down 0.59 percent at 18,345 yen.