Pepsi-Cola North America is to launch two "limited-time-only" extensions to two of its largest soft drinks brands.

The first, Mountain Dew Pitch Black, will launch in late August and stay on store shelves through Halloween. Then, in time for the holidays, Pepsi Holiday Spice will hit stores on 1 November for an eight-week appearance until the end of the year.

Mountain Dew Pitch Black combines the taste of Mountain Dew with black grape flavour. It follows in the footsteps of Mountain Dew LiveWire, which grew the Mountain Dew trademark more than 10% during its inaugural six-month run in 2003.

The brand will be backed by a theatre commercial parodying "B" horror movies. Additional marketing support includes an Internet "Dewsletter" and product sampling at General Growth Properties malls and at this week's ESPN X Games in Los Angeles.

Mountain Dew Pitch Black will be available in 20-oz bottles, 2-litre bottles and 12-packs of 12-ounce cans.

Then in November, Pepsi will launch Pepsi Holiday Spice - Pepsi-Cola with a spicy finish of ginger and cinnamon.

The brand will feature nostalgic package graphics.

Pepsi Holiday Spice will be available in the US for an eight-week period (1 November - 31 December) in 20-ounce bottles, 2-litre bottles and 12-packs of 12-ounce cans.

"People like new products - they're much more interested in variety nowadays than they were just a few years ago," said Dave Burwick, SVP and chief marketing officer of Pepsi-Cola North America. "By introducing new flavours for a short period of time, then taking them away, we're meeting the wants and needs of soft-drink consumers while playing directly to their purchasing patterns."