Tokyo, Japan | Toyota said it will start selling a mug-sized robot called Kirobo Mini as a chatty companion for its human owners.

The 10 centimetre (four inch) tall robot will go on sale next year in Japan for 39,800 yen ($400) after a bigger version of the doe-eyed Kirobo -- roughly the size of a chihuahua -- became the first android to converse with an astronaut in space.

Toyota is usually associated with cars, but it has been investing millions in robotics and Kirobo is its first commercial foray into the sector.

The world's biggest automaker said the robot -- which can carry on simple conversations and respond to emotions -- could help it develop vehicle technology.

"We want to address growing issues in society where people have no one to talk to," said Moritaka Yoshida, a senior managing officer at Toyota.

Kirobo Mini is being showcased at Asia's largest electronics fair, the IT & Electronics Comprehensive Exhibition (CEATEC), which is being held in Tokyo this week.

Kirobo became the world's first robot astronaut after it was flown to the International Space Station in 2013 as a conversation partner for Japanese commander Koichi Wakata.

It was part of a longer-term project to see how a robot could act as a companion for isolated people, particularly to see if it can develop conversational skills.

Japan faces the twin threats of an ageing demographic -- with people over 65 expected to account for nearly 40 percent of the populationby 2060 --- and a dwindling birthrate. 

It has also struggled with the problems of social isolation, most notably the phenomenon of "hikikomori" where people, often teens and young adults, refuse to leave the house or engage socially, instead opting to play video games or remain in their rooms. 

There are a number of Japanese firms selling commercialised robots, including mobile carrier SoftBank which started selling its talking humanoid Pepper last year.