MILAN (Reuters) - Generali Investments, the global investment arm of Italy's top insurer Generali, said on Friday it had signed an agreement to buy a 77% stake in the U.S. investment firm MGG Investment Group for $320 million.

Founded in 2014 by Kevin Griffin and McCourt Global, a private family company, New York-based MGG has over $6 billion in assets under management and provides senior secured loans and structured capital solutions to U.S. middle market businesses. 

The deal is expected to close this year with an estimated negative impact on Generali's Solvency II ratio of two percentage points.

The price may increase upon the achievement of certain operational milestones, Generali Investments said in a statement. 

MGG's investment strategy will not change after the deal and Kevin Griffin will remain as chief executive, the statement said.