TOKYO (AP) -- Four of Japan's leading robot startups joined forces Wednesday, brought together by a common concern that neighboring South Korea could pull ahead in the race to transform robots from science fiction fantasy to commercial success.

Japan, which has long led the world in robo-technology, has created machines that can clean, dance, greet, feed, monitor, relax and befriend. But for all the buzz, so-called ''intelligent service robots'' have been slow to penetrate the average home, which is still more likely to shell out money for the latest flat screen TV than a pricey humanoid.

The companies -- Tokyo's ZMP Inc., Nagoya's Business Design Laboratory Co., Osaka's Vstone Co. and Fukuoka's Tmsuk -- say that new South Korean robot legislation passed earlier this year compelled them to form the ''Association for market creation of the future generation robots'' to cooperate in research, development and marketing.

After a decade of working in isolation, Japanese robot startups now need a broader, more-agressive front to push products to mass market, said Yoichi Takamoto, Tmsuk CEO and chair of the newly formed group.

''The South Korean law was passed, and we realized that if we didn't do anything, we were in trouble,'' said Takamoto, whose company makes the $2,700 ''Roborior'' -- a white, mobile orb on wheels that keeps watch over empty homes and offices.

Indeed, South Korea has embraced robotics with unparalleled national zeal.

The government is aiming to put a robot in every household by 2020, and has mobilized companies and scientists to help integrate robots into Korean society. The country plans to build two robot theme parks by 2013 and even drafted a ''Robot Ethics Code'' last year to prevent robot-human abuse.

In February, the National Assembly passed a bill to spur development and marketing of intelligent robots. The law also established investment firms to provide financial support for robotics manufacturers.

Faced with low birth rates and long life spans, both Japan and South Korea are aging quickly and are turning to robots to replace disappearing workers as well as care for the elderly. The Japanese government paints a dire picture. By 2040, children will comprise 9.3 percent of Japan's population, while the over-65 population will balloon to 36.5 percent.

While Japan has also funded a variety of robotics-related projects, it's been a quieter road for the country's consumer robot revolution.

Takamoto said the new group will initially focus on expanding the market for simple service robots designed to ''hedge risk'' -- keep grandma and grandpa engaged with life, monitor pets, watch children.

The four CEOs gathered in Tokyo pointed to Business Design Laboratory's moonwalker-like ''ifbot'' and ZMP's ''nuvo'' companion as especially popular with seniors in Japan.

Developers are a generation away from true humanoids, and robots for complex nursing care are still bulky and expensive, they said.

''In ten years, robots may be able to help out around the house,'' Takamoto said. ''But I don't necessarily know that robots should do everything.''