* TSX falls 23.37 points, or 0.16 percent, to 14,280.80 * Eight of 10 main index sectors decline * Canadian Natural climbs after results By John Tilak TORONTO, March 6 (Reuters) - Canada's main stock index fell on Thursday as worries about political uncertainty in Ukraine overshadowed positive U.S. labor market data and a gain in Canadian Natural Resources Ltd shares. Figures showed that the number of Americans filing new claims for unemployment benefits dropped to a three-month low last week. Investors saw that as a positive signal ahead of Friday's U.S. nonfarm payrolls report. The market also digested news of Crimea's parliament voting to join Russia and its Moscow-backed government setting a referendum within 10 days on the decision. "It's a little premature to think that the Ukraine situation is over with," said Colin Cieszynski, senior market analyst at CMC Markets Canada. "People were getting complacent about it again, but this thing can flare back anytime." The Toronto market, which is up about 5 percent this year, took a bit of a breather after three straight daily gains. "We're just in a bit of a pause here as we've had a pretty good run lately," Cieszynski said. "But the underlying trends for the TSX remain favorable as resource demand continues to improve." The Toronto Stock Exchange's S&P/TSX composite index was down 23.37 points, or 0.16 percent, at 14,280.80. Eight of the 10 main sectors on the index were in the red. Financials, the index's most heavily weighted sector, declined. Royal Bank of Canada gave back 0.2 percent to C$72.22, and Toronto Dominion Bank lost 0.2 percent to C$50.24. The materials sector, which includes mining stocks, showed the strongest gain, rising 0.6 percent. Potash Corp added 1.7 percent to C$39.03, and Teck Resources Ltd climbed 2 percent to C$25.09. In corporate news, oil producer Canadian Natural reported a rise in quarterly profit, and the stock advanced 0.4 percent to C$40.87. SNC-Lavalin Group Inc's shares dropped 4 percent, to C$46.44, after the company reported fourth-quarter earnings and forecast a profit for 2014 that missed market expectations.