TransferWise is in "preliminary talks" with UK banks about partnering with them to offer TransferWise's international payments service in their banking apps.

TransferWise, one of Britain's few "unicorns" (a private company worth over $1 billion), confirmed the talks as it announced it has signed its first ever partnership deal with Estonia’s largest domestic bank, LHV.

The deal will see TransferWise's service integrated directly into LHV's mobile app. Both the founders of London-based TransferWise are from Estonia.

TransferWise lets people send money internationally online at a radically cheaper rate than offered by traditional high street banks and operators, as shown by the chart from Goldman Sachs below.

Its services are really cheap because it does this by cutting out operating costs like branch networks and using a peer-to-peer matching service that cuts down on transfer fees.

The LHV deal marks the launch of TransferWise's API, tech speak for a digital DIY kit that will let people build TransferWise's service into their own apps and websites.

TransferWise's CEO and founder Taavet Hinrikus says in an emailed statement:

We’re looking forward to being able to help our customers even more by developing integrated solutions with other services and products so that people can access the TransferWise experience through any application from messaging apps to e-wallets. We want to make it as convenient and easy as possible for people to transfer money internationally.

The startup says it is in talks with a number of other banks, both established names and new challenger banks, about launching similar partnerships to the LHV deal. The Financial Times reports that the talks involve UK lenders.

Some of the most ambitious and forward thinking challenger banks in the world are looking to build banks as a platform, where third parties provide services but the bank itself acts as a gateway to the cash and protect a company's identity. Startups pursuing this model include Fidor Bank and Number26, both of which are German.

And even established banks are increasingly looking to outsource services to nimble fintech startups. JPMorgan recently signed a partnership with online lender OnDeck and Spanish bank BBVA has partnered with startup Dwolla to do real-time payments.

TransferWise is one of London's hottest startups, reportedly valued at over $1 billion (£670 million) in a $58 million (£38.9 million) funding round at the start of the year. You can read our profile of the company from October here.