Kingdom Hearts Insider translated a blog that released a new detail regarding the battle system for Kingdom Hearts 358/2 Days:

When the player’s HP drops and the HP gauge turns red, the player can initiate a Limit Break by holding down the A button for a few seconds. During the Limit Break, the player’s speed and attack power increases.

More details about the battle system are expected to arise now that the release date is fast approaching.

Source: Tales @ OK