planning to invest upwards of US$100 million in their mobile payments joint venture, people with knowledge of the project have told Bloomberg News.

The Isis joint venture is owned by Verizon Wireless, AT&T and T-Mobile USA.

The mobile networks may invest hundreds of millions of dollars in the venture -- but only if it gains subscribers -- in an attempt to catch up with the mobile wallet platform unveiled by Google earlier this year.

Isis aims to bring mobile commerce to consumers and merchants by allowing them to use mobile phones to make point-of-purchase sales through the use of near-field communication (NFC) technology.

Earlier this year, Isis announced Salt Lake City, Utah and Austin, Texas as initial launch markets, slated to roll out in the first half of 2012 with support from all four payment networks.