TOKYO, Sept 3 (Reuters) - Japanese shares inched up on Tuesday as a weaker yen propped up exporters, although negative factors including the U.S.-China trade war and Brexit concerns curbed market gains.
At 0153 GMT, Japan's Nikkei share average was up 0.18% at 20,657.81.
There were 157 advancers on the Nikkei index against 62 decliners.
Adding to investor caution already heightened by the Washington-Beijing trade conflict was the prospect of more Brexit-related market turmoil.
British lawmakers decide later on Tuesday whether to move Britain a step closer to an early election, when they vote on the first stage of their plan to block Prime Minister Boris Johnson from pursuing a no-deal Brexit.
With the yen edging further away from an eight-month high against the dollar last week, shares of major exporters advanced.
Toyota Motor Corp climbed 0.8%, Subaru was up 1.7%, Mitsubishi Heavy Industries rose 0.5% and Panasonic added 0.7%.
Nickel-related companies gained as the price of the metal soared to a five-year high due to shortage worries as top producer Indonesia said it would stop ore exports from January 2020, two years earlier than initially flagged.
Sumitomo Metal Mining Co rallied 2.8% and Pacific Metals Co climbed 1.9%.
The broader Topix gained 0.44% to 1,511.82.
The stocks that gained the most among the top 30 core Topix names were Shin-Etsu Chemical Co, which rose 1.7%, and Hitachi, up 1.6%.
The worst performers among the Topix 30 were Fanuc Corp , which lost 1.3%, followed by KDDI Corp, down 0.7%. (Editing by Richard Borsuk)