The GSM Association, a union of 650 GSM mobile phone service operators, on Tuesday asked the Indian government not to allocate spectrum at 1900 MHz to CDMA operators like Reliance as it would restrict the ability of mobile users to roam internationally.

The GSMA urged India to maintain its alignment with the global community and protect the International Telecommunications Union's recommended IMT 2000 core band for Third Generation (3G) mobile services.

"India's regulatory environment has been inconsistent. India, a member of ITU, had previously accepted to reserve spectrum frequencies of 1920-1980 MHz and 2110-2170 MHz for 3G mobile services. Now the regulator (TRAI) wants to slice a part of this and allocate it to Second Generation (2G) operators. GSMA chairman Craig Ehrlich told reporters in Singapore.

"This will undermine growth of telecommunications and restrict international roaming," he said.

The GSMA is asking CEOs of all its member phone companies around the world to write to Telecom Regulatory Authority of India to stop it from doing so.

"Except for the United States, the 1900 MHz spectrum frequency is used for 3G in all the countries. US has been out of step in spectrum allocation for the past 10 years. Operators in the US can't roam," he said.