* FTSEurofirst 300, FTSE 100 both down 0.1 pct * BG leads faller after warning about lower production By Francesco Canepa LONDON, Sept 9 (Reuters) - European shares edged lower on Monday, snapping a three-day rise as heavyweight BG Group led a selloff in the energy sector after warning about production. Shares in BG fell 3.9 percent, dragging the broader European oil sector 0.7 percent lower, after the group said delays at projects in Egypt and Norway would reduce its output in 2014. The stock knocked 6.8 points off Britain's FTSE 100, which was 4.2 points or 0.1 percent lower at 6,543.16 points at 0723 GMT. BG was also the top faller on the pan-European FTSEurofirst 300 index, which was 0.1 percent lower at 1,228.68 points. The FTSEurofirst 300 had risen 1.4 percent in the previous three sessions, helped by expectations of continued monetary support from the European Central Bank and the U.S. Federal Reserve. The ECB reiterated on Thursday it would keep interest rates low to support the region's economy, while weaker-than-expected U.S. jobs data on the following day raised speculation in equity markets that the Fed might minimise or delay a cut in its asset-purchase programme. "Ironically, softer data led to a rally in equities overnight and to the extent that tapering comes later that's certainly better for equity markets in the short run," Grant Lewis, head of research at Daiwa Capital Markets, said. "But if tapering is put off because growth is weaker, ultimately that's not going to be good for equity markets." That view contrasted with the reaction on debt markets, where Bund futures dipped on Monday after 13 of 18 primary dealers in a Reuters poll taken after Friday's data said the Fed would still decide to start reducing stimulus this month. Equity markets have struggled to make much headway in the past month and trading has been choppy as investors positioned for both a stimulus cut by the Fed and a possible U.S.-led attack against Syria, which it is feared could cause a broader conflict in the oil-rich Middle East. A U.S. Congressional debate on Syria could start as early as this week, keeping traders on edge. "There is still major geo-political concern in Middle East, with an attack on Syria almost guaranteed now as the U.S. garners more support," said Ronnie Chopra, a strategist at TradeNext. He expected traders to start selling the FTSE 100 once it reached 6,600 points.