* FTSEurofirst 300, Euro STOXX 50 down 0.4 pct
* Santander weighs on indexes as chairman dies
* ARM falls after Apple product launches
By Francesco Canepa
LONDON, Sept 10 (Reuters) - Europe's leading shares fell for a fourth straight session on Wednesday, with Spain's top lender Santander the biggest drag after the death of its chairman prompted worries over a successor.
Sentiment on the broader market was sapped by the prospect of tighter U.S. monetary conditions, which - along with the wars in Ukraine and the Middle East - has unnerved investors.
EU states will discuss on Wednesday whether to implement new sanctions against Russia over its role in the Ukraine crisis.
Shares in Santander fell 1.7 percent after Emilio Botin, who transformed the firm from a small domestic lender into the euro zone's biggest bank, died of a heart attack on Tuesday night.
The stock knocked nearly 3 points off the Euro STOXX 50 index of euro zone blue chips, which was down 13.01 points, or 0.4 percent, at 3,232.42 points at 0751 GMT.
"He was perceived as the man who built Santander into a global bank," Javier Bernat Valenzuela, an analyst at Beka Finance in Madrid, said.
"He has been the person who has looked after the bank for the last 30 years but you have to realise there will not be significant changes because the bank is pretty well structured."
Apple supplier ARM Holding fell 2.3 percent to feature among top European fallers, tracking a late fall in the U.S. firm's shares after the unveiling of a watch, two larger iPhones and a mobile payments service on Tuesday.
ARM is still up 8 percent from March's five-month low.
"ARM had a big run up to the announcement and I'm wondering whether investors and consumers are just slowly losing interest," Ed Woolfitt, head of trading at Galvan, said,
"The launch was good but really it's more of just the same - faster, slimmer etc - but nothing to really dazzle."
The pan-European FTSEurofirst 300 index fell 0.4 percent to 1,379.93 points, having hit a 6-1/2-year high on Thursday, when the European Central Bank cut interest rates and president Mario Draghi unveiled new stimulus measures.
Asian and U.S. shares fell overnight as markets wagered the Federal Reserve would raise interest rates earlier than expected, sending U.S. bond yields higher and keeping the dollar well bid near 14-month highs against a basket of currencies.
"The U.S. and Asia are not contributing to a positive momentum and the initial Draghi reaction is wearing off," Mike Reuter, a broker at Tradition, said. "With more EU sanctions looming later today we might as well remain (weak)."
Europe bourses in 2014: link.reuters.com/pap87v
Asset performance in 2014: link.reuters.com/gap87v
Today's European research round-up (Editing by Louise Ireland)