SoftBank said Tuesday it has launched a subscription service that lets customers drive a used car at a fixed monthly rate, as it tries to diversify its business portfolio amid slow growth in the flagship mobile phone business.

The Japanese company has set up Carro Japan in Tokyo, a joint venture with Singapore-based online used car retailer Trusty Cars, for the new service.

Carro Japan started the service for corporate customers Tuesday, with an eye to expanding it to individual customers through partnership with SoftBank's group companies such as Yahoo Japan.

The joint venture will utilize artificial intelligence to analyze the used car market so it can offer better deals than what competitors offer, SoftBank said.

The new service is part of SoftBank's efforts to diversify its revenue sources as its telecom operation struggles after the government propelled its push to lower mobile phone fees in recent years.

Demand for used vehicles has been growing as the delivery of new cars has been delayed amid a global chip shortage, SoftBank said.

The mobile carrier now directly competes with leading carmakers such as Toyota and Honda, which offer similar subscription services.

SoftBank holds a 51% stake in the joint venture, while Trusty Cars has the rest.

One of the funds operated by SoftBank Group, the parent of SoftBank, has invested in Trusty Cars, SoftBank said.