MUMBAI/NEW DELHI: The Indian government has asked its biggest state-owned firm, Oil and Natural Gas , to list its overseas unit ONGC Videsh, according to a letter seen by Reuters.The move to float the unit - which has investments in 11 producing assets in countries including Russia, Brazil and Iran - is part of a government push to sell state-assets to raise funds.A listing would also help unlock value in the unit by improving its corporate governance and efficiency, the letter from the Department of Investment and Public Asset Management to ONGC said.The letter, sent last week, did not state how much of ONGC should be offered to outside investors.