The tribunal asked the operators to appeal at a higher court, one lawyer on the case said, after the tribunal split its vote with one in favor of the government and the other in favor of the carriers.

The tribunal's decision was keenly watched by investors in Bharti Airtel (BRTI.NS), Vodafone's (VOD.L) Indian unit and Idea Cellular (IDEA.NS) - the country's top three carriers by revenue - which have managed to offer 3G services in most parts of the country because of the pacts.

In a 2010 government auction, Bharti won 3G bandwidth in 13 of the country's 22 service areas, while Idea gained access to 11 and Vodafone nine.

The telecoms ministry told carriers last December that it was illegal to offer 3G services beyond their allotted zones by mutually agreeing to share their airwaves.

In the same month, the three operators and smaller rivals Tata Teleservices TATASL.UL and Aircel challenged the government order before the Telecom Disputes Settlement and Appellate Tribunal (TDSAT).

(Reporting by Suchitra Mohanty; Editing by Ryan Woo)

• A Permanent Economic Emergency