An attempt by U.S. company LightSquared to set up a 4G broadband service in the frequency band next to one used by GPS satellites may be over, experts say.

LightSquared's plan to build 40,000 ground transmitters to transmit 4G wireless signals in a band at 1525 to 1559 MHz -- right next to the 1559 to 1610 MHz band GPS satellites use to transmit navigation signals -- brought warnings the plan would create GPS dead zones across the United States because of interference.

The Federal Communications Commission gave preliminary approval to LightSquared's plan in January 2010, but a possible fatal roadblock has been thrown up, NewScientist.com reported Monday.

The 2012 Defense Authorization act, passed in December, bars the FCC from approving systems that interfere in any way with military GPS. A report late last year by an FCC working group warned LightSquare's system would cause serious interference.

The concern had been that strong signals near the 4G transmitters would drown out the faint satnav signals reaching the ground, a worry backed up by subsequent tests.

Because the spending act bans approval of the system unless all GPS interference can be eliminated, it could mean the end for Lightsquared's plan.

Mobile carrier Sprint has suspended a planned deal to cooperate with LightSquared on the proposed network until questions about regulatory approval can be resolved, NewScientist.com reported.