* S.Korea-U.S. military exercises heighten tensions
* Sumitomo Metal Mining soars
* Real-estate sector outperforms
TOKYO, Aug 22 (Reuters) - Japanese stocks were nearly flat in choppy trade on Tuesday morning as geopolitical uncertainty kept activity in check while investors awaited the annual Jackson Hole conference this week.
The Nikkei share average edged up 0.1 percent to 19,407.65 in midmorning trade, after traversing negative and positive territory.
The broader Topix added 0.1 percent to 1,597.18.
Traders say that the Japanese market will likely stay thin and directionless throughout the day, and if the Nikkei were to end lower it would mark a fifth day of decline, the longest losing streak since April 2016.
On Monday, volume of the broader market hit a three-month low of 1.40 billion shares, while turnover dropped to a two-month low of 1.753 trillion yen.
Geopolitical tensions simmered as the United States and South Korea began long-planned joint military exercises on Monday, heightening tensions with North Korea which called the drills a "reckless" step toward nuclear conflict.
"Investors are staying on the sidelines amid geopolitical uncertainty. I don't think the market will see a sharp sell-off for now, but the mood is tense," said Isao Kubo, equity strategist at Nissay Asset Management.
He also said that before taking positions, investors would want to wait to see for monetary policy insights from this week's meeting of global central banks at Jackson Hole, Wyoming, where Federal Reserve Chair Janet Yellen is due to speak.
Sumitomo Metal Mining rose as much as 4 percent to more than 2-year high of 1,912 yen after the company said that it plans to install verification facilities for the mass production of high-purity nickel oxide powder to be used in fuel cell electrodes.
Exporters were mixed after the dollar edged up 0.2 percent to 109.13, having recovered from Monday's intraday low near 108.63 yen.
Toyota Motor Corp shed 0.2 percent, Honda Motor Co rose 0.3 percent and Nintendo Co gained 1.1 percent.
Real estate shares outperformed, with Mitsui Fudosan rising 1.1 percent, while Mitsubishi Estate gained 0.8 percent. (Reporting by Ayai Tomisawa; Editing by Eric Meijer)