With Sprint Nextel (S) and Japanese mobile operator SoftBank postponing their merger deal's formal SEC filing date by three more weeks, speculation had risen even higher that the U.S.'s third-largest mobile carrier was preparing to make a counteroffer to lure MetroPCS (TMUS 0.55%) away from T-Mobile USA.

However, such a play is not in the offing, says Reuters, after talking to several people in position to know.

The delay in filing the Sprint-SoftBank proxy statement/prospectus, according to Reuters' sources, was because of ongoing discussions Sprint was having with Clearwire (NASDAQ: CLWR) about interest payments. Sprint also had accounting questions in regard to its deal last month to acquire $480 million worth of spectrum from U.S. Cellular (USM 2.32%).

Sprint said the delay was due to the complex nature of its deal with SoftBank.

The idea of Sprint trying to spirit MetroPCS away from T-Mobile was first floated in early October by several unnamed sources talking to Bloomberg.

That was the second time in a year that Sprint and MetroPCS were named as possible partners. Last February, Sprint's board of directors shot down CEO Dan Hesse's plan to buy MetroPCS for $8 billion. Either the board wasn't crazy about the then 30% premium over MetroPCS share price, or that the deal was pursued in secret -- or both.

But that was before SoftBank came along with its offer to buy 70% of Sprint, an offer that included a much-needed influx of cash -- $8 billion worth -- and Softbank buying up $12 billion worth of existing stock. That deal made a bid for MetroPCS look more doable for Sprint.

Even if no other developments come along to shake up T-Mobile's acquisition of MetroPCS by the time it is expected to finalize the middle of next year, that combined entity would still remain the nation's No. 3 mobile carrier in terms of subscriber size.

The Sprint/SoftBank deal is also expected to be complete by mid-2013.