UPDATE 1-Bharti slashes mobile roaming charges, shares fall

* New bill plan cuts roaming rate by nearly 60 pct

* Shares fall 3 pct; 2nd worst performer in BSE index this yr (Adds details, background, shares)

By Devidutta Tripathy

NEW DELHI, Nov 20 (Reuters) - India's Bharti Airtel (BRTI.BO: Quote, Profile, Research) launched yet another new billing plan on Friday, slashing mobile roaming rates by nearly 60 percent and signalling a tariff war in the world's fastest-growing wireless market was far from over.

The announcement accelerated losses in the shares of Bharti, the country's top mobile operator. The stock fell as much as 3.3 percent but trimmed losses to 2.7 percent at 284.90 rupees by 0825 GMT in a Mumbai market .BSESN that was up 0.3 percent.

The price war, aimed at grabbing new users ahead of fresh entrants waiting in the wings, has raised concerns about telecom firms' profitability. Four new firms, including ventures funded by Telenor (TEL.OL: Quote, Profile, Research) and Etisalat ETEL.AD, are set to start services this year adding to the existing 11 operators.

Bharti's market value has slumped more than a fifth this year to about $24 billion and its stock is the second worst performer in the main index that has risen about 72 percent. Rival Reliance Communications (RLCM.BO: Quote, Profile, Research) has fallen about a quarter in 2009.

Bharti, whose about 115 million users account for more than 23 percent of India's total mobile subscribers, in September cut call charges within its own network to 50 paise (U.S. 1 cent) a minute and in October launched a low-profit per-second billing plan, reacting to competition.

Tata Teleservices [TATASL.UL], the No. 6 operator, was the first to launch per-second billing, deviating from the industry norm of per-minute billing. The offer was a roaring success and the firm has topped the new signings for three months in a row.