SYDNEY, Oct 16 (Reuters) - U.S. wheat futures hit a near 6-year high on Friday, as dry weather in key global producing regions raised supply concerns, pushing the grain towards its third straight weekly gain of about 4.5%. FUNDAMENTALS * The most active wheat futures contract on the Chicago Board Of Trade was up about 4.5% for the week so far, on track for its third straight weekly gain. * Wheat hit a top of $6.22 a bushel as of 0050 GMT, its highest level since December 2014. * The most active soybean futures were down nearly 0.5% for the week, their first weekly loss in three weeks. * The most active corn futures were up nearly 2.5% for the week, their third straight weekly gain. * Argentina’s Rosario grains exchange lowered its estimate of the South American country’s soon-to-be-harvested 2020/21 wheat crop to 17 million tonnes, from 18 million previously, citing dryness and frosts * The U.S. Department of Agriculture reported another 261,000 tonnes of U.S. soybean sales to China on Thursday morning. MARKET NEWS * The dollar was headed for its best week of the month on Friday, as surging coronavirus cases and stalled progress toward U.S. stimulus had nervous investors seeking safe assets. * Asian stocks came under pressure as investors sought safe havens, such as the U.S. dollar, fearing that a resurgence in coronavirus cases and a lack of additional U.S. fiscal stimulus would hobble the world economy.