In a surprise move, Dish Network raised its bid for Clearwire while at the same time – and rather more predictably – criticised the Committee for Foreign Investment in the United States (CFIUS) for approving SoftBank’s acquisition of Sprint, citing national security risks.

In a letter to Clearwire’s board of directors, Dish has offered to buy the US wholesaler for $4.40 per share in cash, trumping Sprint’s latest nominal purchase price offer of $3.40.

It’s a surprise move in that Clearwire admitted last week to not having any “substantive discussions” with the US satellite broadcaster in recent weeks, and that Sprint – which already has a 51 per cent stake in Clearwire – was most likely to seal the deal.

Dish made a $3.30 per share bid for Clearwire in January, beating Sprint’s previous $2.97 per share offer, although Sprint subsequently upped its bid to $3.40 per share.

“The Clearwire spectrum portfolio has always been a key component to implementing our wireless plans of delivering a superior product and service offering to customers,” said Dish boss Charlie Ergen in statement.

Sprint has yet to officially comment on the revised Dish bid, although the third-largest mobile operator in the US described its latest $3.40 offer as “best and final”.

According to a Clearwire spokesperson the company’s special committee would review Dish’s revised bid, although there is apparently no determination as yet to change its recommendation of a Sprint purchase.

Minority shareholder Crest Financial has nonetheless remained critical of the Sprint offer, arguing it undervalues Clearwire.

Dish has also reacted swiftly to news that CFIUS has approved the acquisition of Sprint – subject to certain conditions – by Japan’s SoftBank.

“We believe the US government should proceed with deliberation and caution in allowing assets of national strategic importance – such as the Sprint fiber backbone and wireless networks – to be owned and operated by a foreign company with significant ties to China,” said Stanton Dodge, Dish executive vice president and general counsel.

“Oversight and accountability for these assets are critical at a time when offshore cyber-attacks, including the hacking of weapons systems designs, continue to rise. Congress should take a close look at the CFIUS review process in this instance.”

As part of the CFIUS green light for the deal, SoftBank and Sprint have entered into a so-called National Security Agreement with the US government.

One of the agreement’s provisions, as reported by SoftBank, is that the two companies must appoint an independent member to the new Sprint board of directors, serving as security director, who is approved by the US government.

Dish is sceptical that this measure will be effective.

“While the requirement to have an appropriately credentialed security director approved by the US government is very common to CFIUS agreements,” said Dish in a statement, “it does little to address the practical risks of national security breaches, including cyber-attacks, because hacking on the ground is not often detected in the boardroom”.

Another part of the security agreement is that if Sprint acquires Clearwire, US government parties will have a one-time right “to require Sprint to remove and decommission by 31 December 2016 certain equipment deployed in the Clearwire network”, a clause clearly prompted by Clearwire’s use of kit from Chinese supplier Huawei.

Although Dish says this is a “key provision of the agreement”, it may well never become effective if Sprint does not acquire 100 per cent of Clearwire equity, something that is not likely to happen – maintains Dish – given Crest Financial’s resistance to tender its shares to Sprint.

Dish further points out that the time lag between now and 2016 creates an “immense period of interim vulnerability”.