A group of institutional investors is set to announce a roughly $2.2bn (€1.5bn) cash infusion into Glencore International that could be a precursor to an initial public offering of stock for the closely held Swiss natural-resources trading giant, according to people familiar with the situation.

US private-equity firm First Reserve Corp. will invest nearly $1bn into Glencore, leading a group that includes institutional investors such as mutual funds and other energy-focused funds, people familiar with the matter said. The deal is expected to be structured as a convertible preferred security that could ultimately turn into common stock in the company.