The cash machine is coming to the mobile phone in the UK with a service that will let subscribers check a bank account balance and buy mobile phone minutes anywhere their phones work.

The LINK cash machine network is set to introduce some cash-machine functions on mobile phones through a downloadable application. The service, called MobileATM, will initially provide account balances and soon after will let users add time to a prepaid phone account, according to a statement by Sun Microsystems, a technology partner in the project.

It should work on any mobile network that allows subscribers to download third-party applications, according to Sun.

At the 3GSM Worldwide Congress in Cannes on Monday, Sun will tout its participation in the MobileATM project, the latest service that uses Java software and SIM (Subscriber Identity Module) cards in mobile phones to certify that users are who they say they are. Sun, the creator of Java, is promoting that combination as a new identification system for secure transactions.

"Identity is a valuable asset that the carriers have that they are under-utilising," said Eric Chu, director of Sun's J2ME (Java 2 Mobile Edition) platform, in an interview last week.

The SIM card that comes in every GSM (Global System for Mobile Communications) phone has nearly unbreakable security, and combining that with Java software can form a trusted platform for customers to authenticate their identities before carrying out tasks such as cash-machine transactions, said David Rivas, CTO for Sun's client systems group. The applications can run on a Java virtual machine on the phone, which is secured via a "sandbox" that keeps viruses and other problems out of the software, he said.

The technology offers a number of possibilities, Rivas said. For example, subscribers could start up their phones with a password and then use it, via RFID (radio frequency identification) or another technology, to pay subway fares wirelessly, Rivas said. Even more significant, for larger purchases the phone could act like a credit card, with a Java application popping up a screen for the subscriber to enter a password on the spot, and the phone communicating the authorisation to a cash register, Rivas said.

The service was scheduled for a UK launch in mid-January and a global introduction later in the year. Sun was unable to confirm that the service was launched on schedule, but more information can be found at MobileATM's website.

Mobile operators including SK Telecom of South Korea, NTT DoCoMo of Japan and Globe Telecom of the Philippines already are using Java in personal financial and payment applications for subscribers, according to Sun.

Yankee Group analyst John Jackson says businesses and consumers may well embrace phones as payment devices. "Given the proliferation of cell phones and their computing capabilities, it's a logical extension of what you do today with your debit card," he says.

Two challenges Sun faces in making its vision a reality are achieving consistency across the Java platforms on different phones and establishing a standards-based back-end infrastructure such as the Sun-backed Liberty Alliance, Jackson says.

Peter Sayer in Paris contributed to this report.