India Securities statement to the Bombay Stock Exchange on Wednesday did not give further details.
An Essar Group official said the companies had previously set a March 31 date for getting the necessary approvals, but had to extend it as a court decision on the merger is still pending.
India's Madras High Court will hold a final hearing on April 1, on the petition to merge the two Essar firms, India Securities said last week.
UK-based Vodafone has objected to the merger of the two Essar Group firms, saying India Securities' value may be inaccurately used to calculate the value of its Indian telecoms joint venture Vodafone Essar.