"We need to 'tropicalize' it and make it fit for the Mexican market and regulation," Santander's Mexico country head Felipe Garcia told Reuters in an interview, adding that because the digital bank already operates in Argentina and some European countries the operation will not be starting from scratch.

Mexico was an attractive market for the digital lender because it had a relatively low level of banking penetration compared to other Latin American countries and a very young population, he said, with the launch poised to help integrate more people into the financial system.

Garcia did not say how much Spain's biggest bank would invest in the move.

Santander last month valued its Mexican business at around 8.1 billion euros with the launch of a voluntary tender offer to acquire shares it does not own, a step towards its de-listing.

The unit is Mexico's third-biggest bank by the size of its credit portfolio and managed some 810 billion pesos ($43.23 billion) at the end of last year, according to data from the national banking regulator.

Its shares closed Thursday at 24.20 pesos, a slight gain of 0.12% from the day before.

($1 = 18.7385 Mexican pesos)

(Reporting by Valentine Hilaire and Noe Torres; Editing by Sarah Morland and Jamie Freed)

By Valentine Hilaire and Noe Torres