AT&T’s rival suitor for Straight Path Communications increased its bid to $3.1 billion in an attempt to derail the operator’s acquisition of the company and its 5G spectrum licences.

In a statement, the Straight Path Communications board said the sum constituted a “superior offer”, but the AT&T deal remains valid until any new offer is formally accepted.

The rival bidder gave the company until 10 May to accept the deal.

Today’s offer is the unnamed multinational telecommunications company’s third bid in as many weeks, following an initial offer of $1.8 billion in late April, and an increased $2.3 billion bid made last week.

All of the rival’s proposals are higher than the $1.6 billion deal Straight Path Communications agreed with AT&T in early April.

Terms of the deal grant AT&T three working days to “negotiate a possible amendment of that agreement to match or exceed the bidder’s offer.”

AT&T is yet to issue any public comment on the rival offers since confirming it was assessing its options when it issued Q1 earnings on April 25.

If the 5G spectrum licence holder backs out of the AT&T agreement, the operator will be due $38 million in compensation – a fee the new bidder agreed to cover.

Although the identity of AT&T’s rival for Straight Path Communications is still under wraps, several reports tip Verizon as the most likely candidate.

The bidding war for the company, which Bloomberg identified as the third largest holder of FCC-approved 5G spectrum in the US, follows a race by the US’ leading operators to prepare their infrastructure for 5G roll-out.

Straight Path Communications holds 735 mmWave licences in the 39GHz band and 133 licences in 28GHz, which cover the whole of the US including all of the top 40 markets.