* TSX down 42.03 points, or 0.28 percent, at 15,172.93 * Six of 10 main index sectors fall * Telus, Rogers among top decliners By John Tilak TORONTO, July 7 (Reuters) - Canada's main stock index fell on Monday, pulled lower by a selloff in telecom providers' shares following news of a new spectrum auction and a drop in the energy sector after oil prices slipped. The Canadian government said it will auction more prime wireless spectrum early next year, with more than half the airwaves set aside for newer players that have struggled to win business from the country's three dominant telecom companies. Speculation about an earlier-than-expected rise in U.S. interest rates also soured investor sentiment. A gain in the U.S. dollar prompted declines in bullion's price and gold-mining shares, while the reduction of supply worries in Iraq helped drive the price of oil down to the lowest in a month. The U.S. Dollar Index, which measures the greenback's performance against a basket of major currencies, edged up 0.04 percent to 80.241. Despite Monday's decline, the Toronto stock market is up about 11 percent this year after climbing steadily in the past few months. "This week there's a little bit of a reality check going on," said Youssef Zohny, portfolio manager at Stenner Investment Partners of Richardson GMP Ltd, which manages about C$28.3 billion in assets. "Markets are battling a general perception that (valuations) are pretty stretched," he added. "There is some concern that markets could get a setback and it wouldn't take too much, given the strong rally over the last year." The Toronto Stock Exchange's S&P/TSX composite index fell 42.03 points, or 0.28 percent, to close at 15,172.93. Six of the 10 main sectors in the index were in the red. Telecom shares tumbled 1 percent after the spectrum auction news. Telus Corp dropped 1.6 percent to C$39.28. Rogers Communications Inc fell 1.5 percent to C$42.36. An index of energy producers' shares slid 0.9 percent, with Encana Corp shedding 2.5 percent to C$23.80 and Talisman Energy Inc losing 1.7 percent to C$10.89. The gold-mining sector index fell 0.5 percent, reflecting weakness in the commodity's price. Goldcorp Inc slipped 0.3 percent to C$29.25. (Editing by James Dalgleish and Jan Paschal)