Clearwire, the unprofitable company attempting to build a wireless network across the U.S., fell below $1 in trading Tuesday amid concern that it's running out of money.

The stock fell 9.8 percent to 92 cents at the close in New York, the lowest level since it began trading in March 2007. The shares have fallen 53 percent this year through Tuesday. Analysts are projecting a loss of more than $200 million when the Bellevue company releases its second-quarter results Thursday.

Clearwire relies on Sprint Nextel, its majority owner and biggest customer, for the bulk of its revenue.

For investors, Clearwire's underlying value comes from its spectrum holdings — airwaves that can be used to provide wireless services. Recent telecommunications deals have increased the supply of usable spectrum, raising concern that Clearwire's assets aren't as valuable, said Thomas Seitz, an analyst at Jefferies & Co. in New York.

"The stock is down because they have a funding gap, and the way most investors thought they would fill that funding gap was by selling spectrum," Seitz said.

Verizon Wireless entered a deal last month with T-Mobile USA to swap spectrum. AT&T, meanwhile, is working with Sirius XM Radio to make more airwaves available.

Clearwire had $1.4 billion in cash and short-term investments as of March 31, an amount that isn't sufficient to fund cash-flow shortfalls and interest expense through 2013, according to Dave Novosel, a senior bond analyst at Gimme Credit LLC in Chicago.

The clock is ticking, said Jonathan Schildkraut, an analyst at Evercore Partners in New York.

"While many believe their spectrum has tremendous value, there is a chance that they aren't going to have enough money to get to the point where their spectrum value would be realized," he said.