Software testing by Rakuten’s Indian vendors has been impacted by a lockdown in place there since March 25, a spokeswoman said.
The delay is the latest setback for Rakuten, which was forced to push back the start of commercial services for its mobile network to April.
Rakuten is trying to carve out a share of a market currently dominated by three competitors, and drive traffic to its ecommerce and financial services.
On Thursday, the firm reported growing operating losses at its mobile business. Chief Executive Hiroshi Mikitani has said the network cut costs by using cloud-based software instead of proprietary hardware.
The carrier launched with aggressively low priced plans. But it has fewer base stations than its competitors and numbers trailing incumbents, and Rakuten is paying KDDI Corp for roaming services.
Rakuten has not disclosed how many user numbers it has garnered during the first few weeks since the launch, increasing uncertainty over its performance as the coronavirus halts economic activity across Japan.