Pontiac will discontinue the GT and all-wheel-drive versions of the Vibe wagon after the 2006 model year due to sluggish sales of those models and changes in U.S. emissions standards that would have made them costly to redesign.

Pontiac will continue to offer the base-model Vibe for the 2007 model year. It may bring back the GT and awd versions with the next-generation Vibe, a spokesman says.

In a bulletin to Pontiac dealers Thursday morning, Buick-Pontiac-GMC General Manager John Larson told dealers they had until April and May to put in their last requests for the GT and AWD versions. Larson cited changes to U.S. regulatory standards as the reason.

"These changes would affect key structural components," Larson wrote. "The cost of redesign is prohibitive."

U.S. regulatory policy for 2007 has an ultralow emissions standard that the GT and awd versions did not meet. The base does meet the standard, says a Pontiac spokesman.

Sales also factored into the decision. Pontiac sold 64,271 units of the Vibe last year. That was up 9.1 percent from 2004. But dealers say the base model has accounted for the bulk of those sales.

"The GT and awd are very low-penetrating models right now," says Pontiac spokesman Jim Hopson. "There's still a very good possibility we'll resurrect both of those as we look at the next generation of the Vibe over the next couple of years."

The Vibe is a joint project that GM builds with Toyota Motor Corp. at the New United Motor Manufacturing Inc. plant in Fremont, Calif. Toyota builds the engine. Sources close to Pontiac say the NUMMI arrangement is profitable and the killing of these versions does not indicate that the relationship will end.

Pontiac will produce about 45,000 Vibes for 2006 model year, Hopson says. In July, Pontiac starts production on the 2007 base Vibe.

The base Vibe price starts at $16,990, the awd starts at $19,990 and the GT is $20,665. All prices include shipping.