Update: On Tuesday evening the FCC granted LightSquared a two-week extension to file results of its GPS testing. Jim Kirkland, VP of Trimble and founding member of the Coalition to Save Our GPS, said in a statement that it was "disappointing that LightSquared has misused its control over the process to delay this filing."

"It's time for Lightsquared and the FCC to stop squandering resources and move on to spectrum that does not impact GPS."

On Wednesday morning, Kirkland and other members of the "Coalition to Save Our GPS" will hold a press conference to discuss the delay and other related matters. PCMag will be tuning in, so check back for their latest statements.

Original story: LightSquared's multi-million dollar broadband network ambitions could be derailed, after a government agency said the network blocked GPS signals.

The National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT) reported that LightSquared's broadband wireless transmitters jam GPS receivers crucial to aircraft navigation systems. PNT is expected to submit a report to the Federal Communications Committee by June 15, which will contain a recommendation as to whether or not LightSquared should be deployed commercially.

Reston, Va.-based LightSquared has run a satellite communications network for 13 years, but wants to get into the more popular and profitable land-based cellular business, namely through a 4G LTE network. In January, the FCC approved LightSquared's request to broadcast much more powerful land-based signals than it currently provides. At the time, LightSquared promised to reach 100 million Americans by the end of 2012 and 260 million by 2016.

But the plan was strongly opposed by GPS manufacturers like Garmin and Trimble Navigation, which argued that LightSquared's terrestrial towers would wipe out relatively weak GPS signals that are crucial for aviation and military purposes.

In March, LightSquared agreed to meet with government officials and groups representing the GPS industry. LightSquared committed $20 million to a working group that will address interference issues, and appointed Charles Trimble of the U.S. GPS Industry Council, and Trimble Navigation founder, as co-chair.

LightSquared launched its first satellite last fall, with the backing of Harbinger Capital Partners, a hedge fund, according to the Wall Street Journal. Last Friday, CEO Sanjiv Ahuja revealed to Bloomberg TV that it was talking to Sprint about a network-sharing deal.

For more, see LightSquared's First LTE Modem: Hands On.