* TSX falls 6.49 points, or 0.05 percent, to 12,643.93 * Five of 10 main sectors decline * Gold shares gain 1.3 percent * Canadian Natural slips after analyst downgrade * Western Potash tumbles after stake sale By John Tilak TORONTO, June 3 (Reuters) - Canada's main stock index was little changed on Monday, with strength in gold miners offset by a decline in energy producers, as investors digested sluggish economic data from around the world. U.S. manufacturing activity contracted in May for the first time in six months as new orders slipped and there was less demand for exports. Data also showed euro zone manufacturing contracted last month at a slightly slower pace, while Asian factories lost momentum. A decline in Canadian Natural Resources Ltd, following a downgrade of the stock by Goldman Sachs, further weighed on the market. "The market itself is showing signs of toppiness," said John Ing, president of Maison Placements Canada. "The financials are going sideways at the prospect of higher interest rates, energy seems flat and the golds look like they're going to bounce." The Toronto Stock Exchange's S&P/TSX composite index was down 6.49 points, or 0.05 percent, at 12,643.93. Five of the 10 main sectors on the index were in the red. Gold stocks received a boost after a weaker U.S. dollar lifted the price of bullion. "The gold sector has bottomed," Ing said. "At long last even the gold stocks are participating. That's always an encouraging sign." While the gold group has been hit the most this year, falling about 31 percent, it climbed about 1.3 percent on Monday and helped the materials sector add 0.3 percent. Barrick Gold Corp advanced 1.6 percent to C$22.12, and Goldcorp Inc rose 0.5 percent to C$30.91. But Western Potash Corp declined as much as 12 percent after the mining company sold a nearly one-fifth stake to a joint venture of two Chinese companies, requiring a new issue of shares. Financials, the index's most heavily weighted sector, gained 0.2 percent. Royal Bank of Canada was up 0.3 percent at C$61.72. However, energy shares gave back 0.6 percent, thanks to the weakness in Canadian Natural. The stock lost 2.7 percent to C$30.07 and played the biggest role of any single stock in leading the market lower.