U.S.-based Calamos Investments, which has USD 20 billion under management, and EXIN Partners, a Netherlands-based investor focused on insurance, reinsurance and asset management, are bidding for at least 75 percent of National Insurance.
Calamos-EXIN is competing against three interested Chinese groups: Fosun, Shanghai-based Gongbao and Wintime.
Greek media have reported the deal, which has to close by the end of 2017, could be worth about 800 million euros (USD 882 million).
U.S. Commerce Secretary Wilbur Ross wrote a letter to Greek Prime Minister Alexis Tsipras that called for a transparent sale, a senior banker told Reuters. "It is a strong letter," he said.
"The Secretary is fully supportive of the Calamos-EXIN bid, saying it would be a good start towards improving U.S. investment flows to Greece," said the banker, who asked not to be identified.
Ross's letter was copied to the Greek bank association, National Bank's (NBG) management and the central bank, Bank of Greece, the banker said.
Founded in 1891, National Insurance is Greece's oldest insurer and provides life and non-life insurance products. The company had a 16.6 percent share of the market last year and 2015 net profit of 98 million euros (USD 108.11 million). Read the full story U.S. commerce secretary backs Calamos-EXIN bid for GREEK insurer