* Murata, Alps, Taiyo Yuden underperform
* Nikkei moves away from 2-year high
* TSE corrects Japan Post share inclusion date to Sept. 29
TOKYO, Sept 26 (Reuters) - Japan's Nikkei average slipped slightly on Tuesday morning as tech shares and Apple suppliers declined, tracking their U.S. counterparts overnight, while concerns over North Korea sapped risk appetite.
The Nikkei was effectively flat, down 0.1 percent at 20,377.29 by the midday break, moving away from a two-year high of 20,481.27 hit last week.
Meantime, the broader Topix edged up 0.1 percent to 1,673.99.
North Korea's foreign minister said U.S. President Donald Trump had declared war on the country and it reserved the right to take countermeasures, including shooting down U.S. bombers even if they are not in its airspace.
The escalating war of words between North Korea and the United States lifted investor appetite for the perceived safe-haven yen. The dollar was at 111.76 yen after coming off a high of 112.530 the previous day.
"Although the market has become immune to such geopolitical tensions, as the Japanese market was enjoying gains from last week, the latest remarks have provided a reason to take profits," said Takuya Takahashi, a strategist at Daiwa Securities.
Tracking weak U.S. tech shares, chip-related stocks Advantest Corp and Tokyo Electron Ltd tumbled 2.4 percent and 2.0 percent, respectively. TDK Corp dropped 1.1 percent and Hitachi Ltd shed 1.3 percent.
Apple suppliers Murata Manufacturing Co declined 2.5 percent, Taiyo Yuden stumbled 4.6 percent, while Alps Electric dropped 1.0 percent, after Apple Inc fell overnight following a report that the company had told suppliers to scale back shipments of parts for its upcoming iPhone X.
Bucking the weakness, Nippon Telegraph and Telephone Corp rose 2.0 percent after the company said that it will buy back up to 30 million of its own shares, or 1.5 percent of outstanding stocks.
Japan Post Holdings Co was flat at 1,349 yen after it set the price for its follow-up share sale at 1,322 yen per share, a 2 percent discount to Monday's closing price of 1,349 yen. 1/8
In a rare move, the Tokyo Stock Exchange on Monday corrected the date from which it will include Japan Post shares in the Topix index. It said it would include the shares of Japan Post in the Topix on Sept. 29, changing from Oct. 30 that it initially announced.
The exchange's guidelines say it will add new shares to the index on the share delivery date, which was Sept. 29 for the Japan Post deal, but the exchange made an "anomaly announcement" to allow fund managers and securities firms enough time for index rebalancing.
The TSE said its initial announcement caused confusion among market participants who were preparing index adjustments based on its usual guidelines.
"We decided to change to Sept. 29 after they expressed their concerns," said Kazuhiro Nishimukai, director of information services at the Tokyo Stock Exchange.
(Reporting by Ayai Tomisawa; Additional reporting by Miho Ozawa; Editing by Eric Meijer)