Sprint s , the No. 4 U.S. wireless carrier, is preparing to mortgage a little more than 10% of its wireless airwaves to raise cash, the Wall Street Journal reported on Tuesday, citing people familiar with the matter.

The company, whose majority owner is Japan’s SoftBank Group, believes the airwaves are worth more than $14 billion and will try to raise about $3.5 billion initially, the Journal said.

Sprint could not be immediately reached for comment.

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In November, Sprint signed a $1.2 billion deal for the sale and lease-back of certain leased devices and in April, said it would raise $2.2 billion in cash through the sale and lease-back of certain network assets.

The company had negative cash flow of $3.17 billion in the financial year ended March 31.

The carrier, which has been burning through cash as it faces intense competition for subscribers, has said it aims to slash costs by more than $2 billion this fiscal year.