The benchmark S&P/ASX 200 index was trading 39.26.6 points lower at 3863.9, according to the latest available data. The index closed at a fresh 26-month low despite opening 1.3 percent higher. New Zealand's benchmark NZX 50 index slipped 27.338 points to 3255.373. Major miners were hit the hardest as gold fell to its lowest price in two month20110926T063826+0000 TESCO/EMBARGOED UNTIL 0700 GMT Warren Buffett ups stake in Tesco -source LONDON, Sept 26 (Reuters) - Billionaire US investor Warren Buffett has nudged up his stake in world No.3 retailer Tesco , a person familiar with the matter said, in what could be seen as a vote of confidence in new chief executive Phil Clarke. Buffett's Berkshire Hathway Inc last month bought around 34 million Tesco shares for about 120 million pounds ($185 million), lifting its stake in the British supermarket group to 3.64 percent from 3.21 percent, the person said. Tesco declined to comment. Berkshire Hathaway could not immediately be reached for comment. Earlier this year, Buffett caused a stir by saying he thought Tesco should "look hard" at its loss-making Fresh & Easy chain in the United States. Clarke, who succeeded long-serving predecessor Terry Leahy in March, has laid out a plan for the chain to significantly reduce its losses this financial year and break even towards the end of fiscal 2012-3, and made changes such as introducing fresh bakery products and coffee and testing a loyalty card.