* TSX rises 35.03 points, or 0.27 percent, to 12,783.18 * Nine of 10 main sectors advance * Nexen gains 2.1 percent on U.S. regulator approval * TransCanada falls 1.3 percent after results By John Tilak TORONTO, Feb 12 (Reuters) - Canada's main stock index climbed on Tuesday, led by the energy sector, which was supported by higher oil prices and Nexen Inc after U.S. regulators approved a $15.1 billion takeover of the oil and gas company. Investors also eyed events such as the G7 meeting and the State of the Union address by President Barack Obama. The Group of Seven industrialized nations urged countries to refrain from competitive devaluations, while the market waited for this evening's State of the Union address to look for any signs of lawmakers getting closer to a deal to avert automatic spending cuts due to take effect on March 1. "The market is very quiet. There are a lot of things that are up in the air. People are waiting for news," said Irwin Michael, portfolio manager at ABC Funds. At midmorning, the Toronto Stock Exchange's S&P/TSX composite index was up 35.03 points, or 0.27 percent, at 12,783.18. The index briefly turned negative after opening higher, before moving back into positive territory. Calgary, Alberta-based Nexen said the Committee on Foreign Investment in the United States has approved the takeover of the company by China's state-owned <CNOOC 0883.HK>, removing the final barrier to China's largest foreign takeover. Nexen rose 2.1 percent to C$27.50. "People don't want to see too many snags. You want to see M&A go through," Michael said. "If it does go through, it will encourage others to come in and look for companies." The energy sector, which gained 0.6 percent, was also supported by higher oil prices. Canadian Natural Resources Ltd rose 1.6 percent to C$30.99 and played the biggest role of any single stock in leading the market higher. However, shares of TransCanada Corp slipped 1.3 percent to C$47.61 after it reported a 19 percent fall in fourth-quarter profit due to lower earnings from its power business and reduced contributions from some natural gas pipelines. In other company news, Agrium Inc appointed two independent directors to its board after the Canadian fertilizer maker could not come to terms with U.S. activist shareholder Jana Partners, which wants to break up the company. The stock fell 0.5 percent to C$114.43. The financial sector, the index's weightiest, added 0.2 percent. Manulife Financial Corp was up 0.7 percent, at C$15.39.