* FTSEurofirst 300 index down 0.2 percent
* German energy companies fall sharply
* Autos gain after strong car sales data
By Atul Prakash
LONDON, Sept 15 (Reuters) - European shares extended the previous session's losses on Tuesday, with miners losing ground and German energy firms RWE and E.ON falling sharply after a report saying they needed to set aside more money to shut down nuclear power plants.
The broader market also came under pressure, with nervousness ahead of the U.S. Federal Reserve's policy meeting on interest rates this week.
Shares in both RWE and E.ON fell more than 7 percent after Spiegel Online said the firms were as much as 30 billion euros ($34 billion) short of the money they need to set aside to build a safe disposal site for nuclear waste as part of Germany's exit from nuclear power.
E.ON, however, said that nuclear provisions were adequate.
The STOXX Europe 600 Basic Resources index fell 2.6 percent, the top sectoral decliner in Europe.
"Chinese demand for industrial metals continues to be weak and there are some overcapacities in the mining sector. This is a combination which is negative for the sector," Christian Stocker, strategist at UniCredit in Munich, said.
"Uncertainty about the Fed's likely decision continues. If there is no rate hike on Thursday, it could also give a signal that the Fed has some concerns about the health of the economy."
A Fed announcement is scheduled for Thursday after a two-day meeting at which it will decide whether or not to make its first interest rate increase since 2006.
At 0835 GMT, the pan-European FTSEurofirst 300 index was down 0.2 percent at 1,390.68 points. The index ended 0.5 percent lower in the previous session.
Although the benchmark index is more than 5 percent up from a low it hit late last month, it is down about 14 percent from its peak two months ago, mainly on concerns about the pace of economic growth in China and the prospects of a U.S. rate hike.
On the positive side, the automobile sector rose 0.4 percent after figures showed European car registrations surged 11.5 percent last month as a regional market recovery gathered pace.
Europe bourses in 2015: link.reuters.com/pap87v
Asset performance in 2015: link.reuters.com/gap87v
Today's European research round-up
Editing by Mark Trevelyan