India’s fourth largest operator Reliance Communications (RCom) and smaller rival Aircel, which started discussing a merger in December, have again extended the exclusivity period for talks, following “substantial progress”.

The operators pushed the date back for discussing combining their mobile operators by 30 days to 22 June, the Economic Times reported. This is the second delay. In March they extended the talks by 60 days. In February RCom and Aircel’s majority owner Maxis reportedly agreed to a 50:50 ownership structure if a deal is finalised.

A merger would give the joint entity 188 million mobile connections, pushing it ahead of current number three Idea Cellular, which has nearly 174 million connections, but slightly behind number two Vodafone India with 197 million. Market leader Bharti Airtel has about 250 million connections.

RCom last year also struck a deal to acquire Sistema Shyam Teleservices, for approximately $690 million. The merger will give RCom an additional nine million customers and INR15 billion ($229 million) in annual revenue.

In April Aircel agreed to sell Airtel 4G spectrum in eight service regions for INR35 billion ($525 million), which will give it a nationwide 4G footprint to match newcomer Reliance Jio’s pan-India coverage. The sale will enable Aircel to reduce its INR180 billion debt by about INR40 billion prior to the planned RCom merger.