New Delhi, Sep 10 - State-run power utility NTPC may sign an agreement to buy natural gas from Mukesh Ambani-run Reliance Industries (RIL) at the government-approved rate of $4.20 per unit for plants other than Kawas and Gandhar, Power Secretary H.S. Brahma said Thursday.

'In all likelihood, NTPC will sign the Gas Sales and Purchase Agreement (GSPA) with RIL by this month-end,' Brahma told reporters on the sidelines of a conference organised by the Federation of Indian Chambers of Commerce and Industry (FICCI).

This gas will be for plants other than Kawas and Gandhar, he said.

NTPC, however, will continue to fight its legal battle with RIL for gas from the D6 block of the Krishna-Godavari basin at $2.34 per unit for the Kawas and Gandhar plants, a company official said.

NTPC had last Saturday moved the Supreme Court challenging a Bombay High Court order that had permitted Reliance Industries to amend its petition on the ongoing Krishna-Godavari gas row.