UPDATED Oct. 13 at 12:38 p.m. EDT

BRUSSELS — The European Commission, confirming satellite industry fears, has decided to allow terrestrial broadband operators to use a portion of C-band spectrum that had been reserved exclusively for satellite use, a senior commission official said Oct. 9.

The decision is likely to tip the position of the broader grouping that represents European governments at the International Telecommunication Union (ITU) as it prepares for the upcoming World Radiocommunication Conference (WRC) in late 2015.

More immediately, the decision is all but certain to affect the outcome of a WRC preconference of more than 100 governments scheduled for Oct. 20-Nov. 7 in Busan, South Korea, which will set the agenda for WRC-15. It now appears likely that the C-band issue will be placed on that agenda.

One satellite industry official said the decision, which was first articulated in 2008, should be viewed in a positive light insofar as the commission is also committing to preserving an adjacent block of C-band spectrum for satellite use. That upper portion of C-band spectrum also is coveted by terrestrial broadband operators.

Yet to be determined is how the European representatives will present their decision to their counterparts in Latin America, Africa and Asia, where the use of C-band for essential telecommunications services and television is widespread.

“Our worry is that whatever Europe says, other nations will take note of the fact that European governments think half the C-band downlink spectrum now allocated to satellites should be opened to terrestrial broadband despite efforts to demonstrate that it causes interference with the satellite signal,” said an official with one European satellite operator. “The terrestrial guys will use this to the maximum extent possible.”

Roberto Viola, deputy director general for the European Commission’s DG Connect division, said the commission’s decision to open up the lower part of the C-band spectrum, between 3.4 and 3.8 gigahertz, to terrestrial wireless operators might need “harmonization” to protect against interference.

But in an address to a conference on satellite frequency interference and spectrum allocation here organized by the French International Foreign Affairs Institute and the Secure World Foundation, Viola said the decision was final.

The upper half of the band, from 3.8 to 4.2 gigahertz, he said, would be protected as Europe prepares for the ITU’s Plenipotentiary Conference in Busan.

“We have fixed the so-called C-band problem,” Viola said. “It’s a good starting point for coexistence” between satellite and terrestrial networks.

In Europe, like in the United States, C-band satellite transmissions, while still widespread, are nowhere as prevalent in the overall telecommunications landscape as they are in Latin America, Africa and parts of Asia.

The commission “has no appetite” for removing the protections afforded to satellite transmissions in the upper part of the band, Viola said, “and we will make this clear at the upcoming radio conference.”

One of the difficulties the satellite industry has had in defending the C-band allocations against encroachment by more-powerful terrestrial transmissions is that so many C-band receive-only antennas in the developing world are not registered. Neither local nor international regulations required registration, meaning that satellite operators have been left to guess as to how many are in service.

Nigel Fry, head of distribution at the BBC World Service Group — which distributes programming over multiple terrestrial and satellite platforms — said less than 2 percent of the C-band receivers used by BBC’s audience are registered. The total number is estimated in the hundreds of thousands worldwide.

Fry said that, like the BBC, many European broadcasters and satellite fleet operators do substantial business outside Europe and will be affected by any move to invite terrestrial broadband into C-band.

Measures can be taken to compensate for fixed terrestrial services, Fry said, but allowing mobile broadband into C-band “will be disastrous” to the satellite links. “We can coexist with the fixed services, all it takes is some work. But sharing with [terrestrial] mobile is a bridge too far,” he said.

Various satellite-sector groups are now mobilizing for the Busan meeting and for the WRC-15 conference. Armed with studies purporting to show that terrestrial wireless does not use all the spectrum already allocated to it, and calling into question the spectrum-demand growth alleged by terrestrial wireless networks, satellite groups hope to hold the line on C-band encroachment.

Cecil Ameil, senior manager for European affairs at satellite fleet operator SES of Luxembourg, said the several hundred megahertz of contiguous C-band spectrum is a natural target for terrestrial wireless operators.

Proposals that C-band satellite customers outfit their antennas with filters to protect against terrestrial emissions will not work, Ameil said.

Each filter costs hundreds of dollars. Asking hundreds of thousands of consumers to purchase and install them is unrealistic, Ameil said.