Isis is set to launch its mobile payments service in two US cities in September. The launch date was revealed by Doug Bergeron, CEO of terminal maker Verifone which is supplying equipment for the launch in Austin, Texas, and Salt Lake City Utah, during an interview with CNet. Isis has previously said it would launch its service in the summer so a launch was known to be imminent.  It has not officially confirmed the September launch.

Meanwhile the joint venture’s strategy of negotiating with individual card issuers for their inclusion in the Isis wallet is under attack from rival Google. “We don’t think that model is scalable for the simple reason I mentioned earlier that there are 8,500 issuers in the US and literally it will take them a lifetime to work through negotiations with all these issuers,” said Robin Dua, the company’s head of product management, consumer payments and wallet.

Ironically, Google used the same approach as Isis until its move in early August to a cloud-based approach which enables consumers to add any credit or debit card to the company’s wallet. Google had previously struggled to sign up card issuers. Dua said the time for negotiating and then integrating a single card issuer was between six and 12 months under Google’s old model, which is the one being used by Isis.

Dua also addressed Google Wallet’s lack of partners from among mobile operators. It currently only works with Sprint among the biggest US operators, as well as MVNO Virgin Mobile. The country’s three leading operators (AT&T, Verizon Wireless and T-Mobile USA) are partners in Isis. “We are looking to expand carrier distribution  and are in discussion with a number of other carriers today and hope to make announcements in a little while,” said Dua, without supplying a more definite timeline. Given their involvement in Isis, Google is unlikely to partner with the leading operators, leaving smaller operators or MVNOs as possible partners.