TOKYO – Sony’s upgraded portable video game machine PlayStation Vita is going on sale in Japan on Dec. 17, with 26-game software going on sale on the same date, but it won’t be available overseas until next year.

The launch of the PlayStation Vita coincides with Japanese rival Nintendo Co. going on the offensive with new game titles for its portable 3DS, which did not go on sale in time for last year’s holidays.

Sony has already said the Vita won’t be ready in the United States or Europe until next year. The company did not give overseas sales dates, and said such details were undecided.

Hiroshi Kawano, head of Sony Corp.’s gaming unit, Sony Computer Entertainment, announced a Japan link with major mobile carrier NTT DoCoMo for the PlayStation Vita, including a prepaid data reception plan of a 100 hours at 4,980 yen ($65).

During his nearly two-hour presentation at a Tokyo event hall, Kawano repeatedly stressed Sony was serious about pushing the Vita, which he said was targeting casual gamers playing on cellphones as well as hard-core fans who own PlayStation 3 home consoles.

In the past, Nintendo, which makes Super Mario and Pokemon games, has typically beaten Sony offerings in portables.

But Nintendo’s latest offering, the 3DS, which features glasses-free 3-D imagery, has gotten off to a relatively slow start, at 4.32 million sold so far around the world.