Verizon Communications will sell thousands of mobile phone towers to digital infrastructure firm Vertical Bridge in a $3.3 billion deal, it said on Monday, unlocking more cash for the dominant US wireless carrier to bolster its network. The deal, covering 6,339 towers across all 50 US states and Washington D.C., includes upfront cash proceeds of $2.8 billion. The towers will be leased back to Verizon for 10 years, with an option to extend the term up to 50 years. The sale is expected to close by the end of 2024 and would aid Verizon's efforts to drive down tower-related costs. The wireless carrier already has a tie-up with Vertical Bridge, under which the infrastructure firm plans to construct towers with Verizon as the anchor tenant. Vertical Bridge, which operates as a real estate investment trust, has more than 500,000 sites in the US that includes wireless and broadcast towers. It also has partnerships with companies including AT&T and T-Mobile US.