Spanish bank Banco Santander's Argentine unit, Banco Santander Rio SA , filed with U.S. regulators on Friday to withdraw its initial public offering.

In a filing with the U.S. Securities & Exchange Commission, the unit of Europe's second-largest lender said it decided not to pursue the proposed offering at this time.

The company had made its initial IPO filing in May last year, and was looking to raise up to $100 million (63 million pounds) through the offering.

A week before it filed for its IPO, Thomson Reuters news service IFR had reported that Santander's listing of its Argentine subsidiary could bring in as much as $1 billion.

The bank was looking to list American Depository Shares on the New York Stock Exchange, and had hired BofA Merrill Lynch, JP Morgan and Spain's Santander to underwrite the offering.

Banco Santander Rio SA, the largest private sector bank in Argentina, planned to use proceeds from the offering to expand its branch and ATM network, bulk up its portfolio and for acquisitions, according to its initial filing.

(Reporting by Aman Shah in Bangalore; Editing by Roshni Menon)