With sales of the Nintendo 3DS in Western territories in decline, Nintendo is rumoured to be planning a major new peripheral to improve the experience and kickstart sales.

A joystick add-on, which will give the 3DS dual analog controls, is expected to be revealed at a Tokyo trade show next month, where Nintendo plans to reveal other new products and new games for the handheld.

The rumour spawns from French technology blog 01Net, but other news sources suggest that the analog stick won’t just be a standalone peripheral but will be built into a new 3DS model due to launch in 2012.

It seems too early in the handheld’s life-cycle to implement such major changes, but with plenty of noise being made about PlayStation Vita, which offers a core gaming experience and a variety of control methods, the addition of an analog stick would make it easier for developers to create games across both platforms.

The announcement on the future of the Nintendo 3DS is set to take place in Tokyo on September 13, 2011.