* Bank takes total control of asset management unit
* Explores at the same time sale and IPO of Allfunds
* Intesa Sanpaolo considers sale of Allfunds stake (Adds Intesa Sanpaolo statement)
By Pamela Barbaglia and Jesús Aguado
MADRID/LONDON, Nov 16 (Reuters) - Banco Santander agreed on Wednesday to buy back a 50 percent stake in its asset management unit from U.S. buyout funds Warburg Pincus and General Atlantic and explore alternatives for the sale of its Allfunds Bank mutual platform.
The deal, for an undisclosed price, will give Santander full control of its asset management division which operates in 11 countries in Europe and Latin America with 170 billion euros ($181.54 billion) of assets under management.
The asset management business, based on stable returns and higher fees than the core banking activity, offers interesting prospects for Santander which, like other banks in the euro zone, is struggling to revamp earnings in an era of ultra-low interest rates.
The euro zone's second-biggest lender by market value also said it would explore with the two buyout firms a potential sale or stock market listing of the Allfunds unit, which has more than 200 billion euros of assets under management.
Santander Asset Management and Italy's Intesa Sanpaolo each own 50 percent of Allfunds.
Intesa Sanpaolo, Italy's biggest retail bank, said on Wednesday it was considering a sale of its stake.
"The bank has today entered a process aimed at the possible sale of its stake in Allfunds Bank," the lender said.
Intesa holds the stake through its asset management unit Eurizon Capital.
Reuters reported earlier this month that several buyout funds including a consortium of Bain Capital and Advent had approached Santander Asset Management over a possible takeover of Allfunds.
Santander said on Wednesday it expected the asset management deal, including the potential sale of Allfunds, to have a positive impact of above one percent on its earnings per share (EPS) in 2018 and expected the transaction to generate a return on invested capital (RoIC) of above 20 percent in 2018 and of above 25 percent in 2019.
The bank also estimated a negative impact from the transaction on its core equity tier 1 ratio of about 11 basis points at end of 2017.
A source familiar with the matter said Warburg Pincus and General Atlantic decided to sell their shares in Santander Asset Management after a long-awaited deal between UniCredit and Santander to merge their fund management businesses was called off earlier this year.
The source said the two private equity funds, which bought a combined 50 percent stake of Pioneer in 2013, have made returns of about 30 percent each on their investment.
Santander Asset Management was valued at 2.047 billion euros in 2013.
Warburg Pincus declined to comment while General Atlantic was not immediately available for comment.
$1 = 0.9364 euros Additional reporting by Stephen Jewkes, editing by Rachel Armstrong, Julien Toyer and Adrian Croft