LONDON (Reuters) - Vodafone said it would put its 50% stake in Cornerstone, its UK towers joint venture with Telefonica, into its new European infrastructure unit Vantage Towers after reaching a new commercial agreement with the Spanish company. Cornerstone will be the preferred supplier of new tower sites for the two mobile operators’ UK units for an initial eight years from the start of this month with three eight-year renewal periods under the new deal, Vodafone said on Monday. Vodafone spun out its European towers last year to take advantage of investor appetite for infrastructure assets, which offer a long-term secured income stream. It plans to list the unit in Frankfurt in the coming months, and will use the proceeds to reduce its debt. Vodafone’s 50% stake in Cornerstone would add 62 million euros ($75.5 million) to Vantage Towers’ pro forma financial year 2020 adjusted core earnings after leases, Vodafone said. ($1 = 0.8208 euros)