* FTSEurofirst and Euro STOXX 50 both steady
* Altice rises on Cablevision deal
* Fed rate decision due at 1800 GMT
By Sudip Kar-Gupta and Danilo Masoni
LONDON/MILAN, Sept 17 (Reuters) - European shares were steady at midday on Thursday, with renewed dealmaking activity lifting telecoms company Altice, while many investors refrained from taking up big positions before the U.S. Federal Reserve's interest rate decision.
The pan-European FTSEurofirst 300 index and the euro zone's blue-chip Euro STOXX 50 index were both trading almost flat.
Despite caution ahead of the U.S. rate decision due at 1800 GMT, which could see the first hike since 2006, M&A activity continued to surface, driven by large piles of corporate cash and expectations acquisitions will not get cheaper.
"Liquidity makes possible the impossible," Ifigest fund manager Roberto Lottici said. "Yet the global economy battles to grow and the best thing the Fed can do is keep rates steady but clearly set the path for a hike in the coming months."
The latest poll by Reuters, on Wednesday, also showed the majority of economists now expect no hike, although it remains an extremely close call.
Altice shares rose as much as 10 percent, as the company agreed to buy U.S. cable TV operator Cablevision in a deal worth $17.7 billion, including debt.
"Cablevision is ripe for taking out. It's the fourth-largest cable operator in the U.S. and would give Altice access to the highly attractive North East corridor," said Gary Paulin, co-founding partner at brokerage Aviate Global.
Phoenix Group rose 0.4 percent, after initially gaining almost 3 percent after confirming talks to buy Guardian Financial Services. The Altice and Phoenix planned deals came a day after brewer ABI approached rival SAB Miller .
Asian stocks edged up to a three-week high on Thursday while the dollar drifted lower against other currencies as investors consolidated positions before the Fed's decision.
Observers of the Fed see the outcome as a close call given some upbeat recent U.S. data but persistent economic risks as well, such as a slowdown in China.
Harry Shann, investment manager at Logic Investments, remained upbeat on European stock markets in spite of the risks posed by any move by the Fed to raise rates on Thursday.
Shann pointed to economic stimulus measures from the European Central Bank as helping to underpin European equities, along with the prospect that China itself could also undertake similar steps to prevent any slowdown in its economy.
Europe bourses in 2015: link.reuters.com/pap87v
Asset performance in 2015: link.reuters.com/gap87v
Today's European research round-up (Editing by Hugh Lawson and Susan Fenton)