Nintendo is cutting the prices of its older handheld game systems, the Nintendo DSi and the Nintendo DSi XL, on Sept. 12 as it clears the way for the introduction of its new 3DS game system later this year.

The Japanese video game company is cutting $20 off the price of both units. The DSi will sell for $149, down from $169, and the DSi XL (which has a larger screen) will be $169, down from $189. The DS Lite model will remain unchanged at $129.

The DS family of handhelds has been the most successful portable gaming device to date, with more than 133 million units sold since 2004. About 42.3 million have been sold in the U.S. But Nintendo is facing pressure from competitors such as Apple’s iPhone and iPod Touch, which are similarly priced but offer lots of low-cost game apps.

“We know shoppers want to get the maximum value out of every dollar they spend,” said Cammie Dunaway, Nintendo of America’s executive vice president of Sales & Marketing. “Our new Nintendo DSi prices make it easier than ever for consumers to access the tremendous variety of games, applications and social tools on the Nintendo DSi and Nintendo DSi XL systems.”

Nintendo is launching a 3D version of the DS, dubbed the 3DS, sometime this fall.