Ericsson will launch mobile phone banking services, it said on Wednesday, hoping to capture a big chunk of a market it estimates will be worth an annual 20 billion euros ($27.7 billion) by 2015.

Ericsson, the world's biggest mobile telecom equipment maker, said up to 1 billion people worldwide had mobile phones, but no bank account and would benefit from services such as money transfers.

Different estimates we have done ... indicate that the value of revenues from financial services over mobile channel will be around 20 billion euros in 2015, Semir Mahjoub, Head of Ericsson Money Services, said.

We expect to have a reasonable share of this market.

The service will be a rival to traditional money transfer operators like Western Union and MoneyGram initially, but could replace credit cards in the future.

Ericsson said mobile payments and person-to-person money transfers are likely to become some of the most-used mobile applications in many countries in the next two or three years.

Mahjoub said that Ericsson saw such transactions totaling around 600 billion euros by 2015.

While Ericsson has initially partnered with a bank to provide the service in Europe, it hopes its global presence will mean it can sell the service to telecoms operators internationally and connect them in a cross-border system.

Given our global presence, which is our main asset in this case, we are working with mobile operators and delivering similar systems to them already, we hope to be able to capture a reasonable share of this market, Mahjoub said.

There are not many other companies that will be able to do this on a global scale. There will be others, but not many.

(Editing by Elaine Hardcastle)