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* Comey dismissal, North Korea unnerve investors
* Minebea jumps on strong forecast
By Ayai Tomisawa
TOKYO, May 10 (Reuters) - Japanese stocks edged up to hover at 17-month highs as a weak yen trend supported sentiment, but gains were limited by fears arising from U.S. President Donald Trump's sacking of his FBI director and North Korea's nuclear programme.
The Nikkei share average rose 0.5 percent to 19,938.53 in mid-morning trade, the highest since December 2015, after it dipped 0.3 percent on the previous day.
The dollar is down 0.2 percent against the yen to 113.77 yen , below its overnight high of 114.325, but traders said that investors are comfortable with that level as the dollar is well above its recent lows.
Analysts said that the Nikkei was seen as well placed to eventually top the 20,000 threshold thanks to the weak yen which would push up Japanese exporters' earnings.
But at the same time, with Japanese stocks gaining sharply in a short period of time, investors have become cautious about chasing the market higher, they said.
Also making investors nervous was news that U.S. President Donald Trump abruptly fired FBI Director James Comey.
Comey had been leading his agency's investigation into alleged Russian meddling in the 2016 U.S. presidential campaign and possible collusion with Trump's campaign. Democrats immediately accused Trump of acting out of political motives.
Rekindled fears that North Korea could be gearing up for another weapons test also sent investors to the sidelines.
"This news could trigger yen buying, but for now, as the dollar-yen is stable, there is a limited direct impact on the Japanese market," said Seiki Orimi, a senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
North Korea's ambassador to Britain, Choe Il, set a defiant tone in an interview with Sky News, saying his country would continue with its nuclear and missile programmes and conduct its sixth nuclear test "at the place and time as decided by our supreme leader, Kim Jong Un."
Companies with strong earnings and forecasts gained. Minebea Mitsumi Inc jumped 11 percent after saying it expected a 14 percent rise in its operating profit for the year through March 2018.
Mitsubishi Motors Corp surged 7 percent after forecasting a near 14-fold rise in operating profit for this fiscal year.
Toyota Motor Corp and SoftBank Group are expected to release results after the market close.
The broader Topix rose 0.3 percent to 1,586.02 and the JPX-Nikkei Index 400 gained 0.2 percent to 14,159.38. (Editing by Eric Meijer)