A number of reports on Wednesday claimed that Sprint (S) was cooking up an offer to acquire the remaining shares of wireless broadband wholesaler Clearwire, and the company has just made a formal bid. Reuters on Thursday reports that Sprint has offered $2.90 a share, or $2.1 billion, for the 48.3% of Clearwire Sprint does not already own. The offer represents a 5% premium over Clearwire shares as of Wednesday’s close, and the deal would value Clearwire at $4.2 billion. If the bid is accepted, it would only occur following Softbank’s successful purchase of a 70% Sprint stake, and it would also need regulatory approval, of course.