An anonymous “multi-national telecommunications company,” believed by many to be Verizon, once again raised the stakes in the Straight Path bidding war with an offer of some $3.1 billion.

Straight Path reported the latest salvo in the bidding back and forth on Monday, noting the mystery player submitted an offer of $184 per share – for a total value of around $3.1 billion. That’s up from its last offer of $135.96 per share – or $2.3 billion – that was submitted in the middle of last week.

The continually rising cost comes as the anon player seeks to oust AT&T as the heir-apparent to Straight Path’s 28 GHz and 29 GHz spectrum holdings. Those airwaves are widely expected to be key bands for future 5G wireless service given the massive amounts of open bandwidth available at those frequencies. So it’s no surprise that the latest proposal is nearly double the $1.6 billion price named in AT&T’s original merger agreement with the spectrum company announced last month.

Once again, AT&T has three business days to come back with an equal or better offer. If it fails to do so and Straight Path opts for the higher bid, it will have to hand over a $38 million termination fee to AT&T.

Straight Path currently holds 735 millimeter wave licenses in the 28 GHz and 39 GHz bands, which amount to an average of 620 MHz in the top 30 U.S. markets. The holdings represent about 95 percent of the commercially available 39 GHz spectrum licenses, CEO Davidi Jonas has said previously. Its 28 GHz airwaves also blanket key markets like New York and San Francisco, he said.

Back in January, the FCC gave the company 12 months to unload its spectrum assets as part of a settlement. More on that can be found here.