Sprint is said to be preparing its official offer to purchase smaller rival T-Mobile US. Bloomberg reports that Sprint executives have met with up to six banks in recent months to make sure that financial details around the potential deal are solid when it formally puts in a bid. The merger has been rumored for months, with SoftBank CEO Masayoshi Son routinely expressing interest in T-Mobile; John Legere could lead the combined company Son has promised to launch a pricing war with larger competitors ATT and Verizon Wireless if regulators approve the deal.