* Nikkei has dropped 4.3 pct over past four sessions

* Topix falls to lowest since mid-February

* Communication sector helped by SoftBank Corp, Yahoo Japan

By Ayai Tomisawa

TOKYO, May 9 (Reuters) – Japan’s Nikkei fell for a fourth day to a six-week low as investors remained cautious ahead of the next round of U.S-China trade talks, while SoftBank Corp and Yahoo Japan were under the spotlight after their alignment news.

The Nikkei share average was down 1.2 percent to 21,334.13 at the midday break, after falling as low as 21,315.07, its lowest since March 29.

The Nikkei has shed 4.3 percent over the past four sessions.

U.S. President Donald Trump has threatened to impose additional tariffs on Chinese goods beginning on Friday, while