 "Coal India officers to go on strike over pay-related issues")
The state-owned company, the world's No. 1 coal miner that accounts for about 80% of India's output, frequently falls short of its output target due to employee strikes, delays in getting approvals to expand mines and other issues.
As a result, India is the world's third largest importer of coal despite sitting on the fifth-largest reserve.
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"Coal Mines officers' Association of India has served a strike notice ... against non-finalisation of performance related pay, new pension scheme and other demands," the company said in a statement to the Bombay Stock Exchange on Wednesday.
"Efforts are being made to reconcile the same."
Though Coal India's production peaks in March, not all of its output will be hit as only 19,000 of the total 349,000 employees are of officer rank, two company officials said.
"There will of course be some amount of dent but we do not expect it to be a total halt of mining across the company," said one of the officials, who declined to be named as he is not authorised to speak to media.
A Coal Ministry spokesman could not be immediately reached for a comment.
In the eleven months to February, Coal India produced 409.13 million tonne, or 95% of its target for the period. A labour protest in December had cut off supply of about 200,000 tonne per day for almost a week, mostly to power generators.
Chairman S Narsing Rao told Reuters last month that the company expected to produce about 475 million tonne in the fiscal year ending March 31 and raise it by 30% next year.
India's coal imports rose 21% to 152 million tonne in 2013 calendar year, according to research firm OreTeam.
Coal India shares have shed more than 10% so far this year, extending last year's losses of 18%.