* Nikkei slips after five-day winning streak * Seen as much needed adjustment after 20 pct gain this yr * Exporters and China-related shares tumble By Mari Saito TOKYO, March 21 (Reuters) - Japan's Nikkei average slipped 0.3 percent on Wednesday, moving away from 8-1/2 month highs after fresh concerns about China's economic growth pushed U.S. stocks lower, though market players said a softer yen underpinned sentiment. The drop broke a five-day winning streak but was seen as a welcome adjustment as the index has soared nearly 20 percent this year on the back of a run of robust U.S. economic data and liquidity boosting programmes by global central banks. "The Nikkei is in a slight adjustment, a much needed one for investors who have largely missed this year's rally," said Kenichi Hirano, operating officer at Tachibana Securities. "But the Nikkei is finding strong support and if it doesn't fall below 10,000 today, investors who have been waiting for a dip will be forced to buy at this level," said Hirano. The benchmark Nikkei slipped 31.97 points to 10,110.84, easing from an 8-1/2-month high of 10,172.64 marked on Monday. "The focus today will be on whether the Nikkei can hold the 10,100 level in the morning session and then to see how it reacts to Chinese markets in the afternoon," said Masayuki Doshida, senior market analyst at Rakuten Securities. Investors took profit in major exporters, which have logged robust gains this year. Toyota Motor Corp fell 1.4 percent, Nissan Motor Co sagged 2.7 percent, and Sony Corp tumbled 2.2 percent. Stocks with heavy exposure to China also fell in heavy volume, with construction machinery maker Komatsu Ltd down 2.4 percent and industrial robot manufacturer Fanuc Corp easing 0.3 percent. The Nikkei China 50 index fell 0.97 percent. Hirano said domestic institutional investors, who had been net sellers this month as they headed into the end of the financial year at the end of March, had now finished with their planned selling. The broader Topix index declined 0.5 percent to 864.96. Wall Street fell after global mining giant BHP Billiton said it saw signs of "flattening" iron-ore demand from China, the world's top metals consumer, which weighed on commodity markets and energy shares. Japan's mining and oil and coal sectors were the worst performers on the main board, falling 1.7 and 1.9 percent respectively. A softer yen was expected to continue to support the market as was U.S. economic data which remained robust in February, with permits for U.S. homebuilding nearing a 3-1/2 year high last month. The euro was last trading at 110.85 yen on the EBS platform, while the greenback was at 83.640 yen.