Tesla CEO Elon Musk and CFO Deepak Ahuja said the biggest factor hampering deliveries of the Model X is the supply of components for the SUV's second-row seats.
"To eliminate these supply constraints and achieve a better overall outcome, we have brought manufacturing of these seats in-house," they wrote. "In addition, we and some of our other Model X suppliers are still ramping up and fine-tuning production. These factors add uncertainty to our build plans during Q4, but we feel emphasizing quality is the right decision for our customers."
The second-row seats move independently on tracks to give occupants easier access to the third row.
Tesla said it expects average production and deliveries of 1,600 to 1,800 vehicles per week for the Model S sedan and Model X combined during 2016.
"We expect our average vehicle sales price to increase slightly in Q4 with more deliveries of highly optioned Model X vehicles," the letter said.
It also noted that Tesla plans to launch a "lower-priced version of Model X with a smaller battery pack during 2016."
Pricing on that version was not announced.
"Since the Model X launch event, order rates have accelerated for both Model S and Model X," the letter said. "Although it is too early to draw firm conclusions, this supports our belief that Model X expands the market for Tesla vehicles, with little to no cannibalization of Model S."
Tesla delivered a record 11,603 new vehicles in the third quarter. In the fourth quarter, it plans to build 15,000-17,000 vehicles, which will result in 50,000-52,000 total deliveries for the year, down slightly from its mid-year forecast.
Edmunds says: Car shoppers who are anxious to get their hands on the Tesla Model X get some reassuring words from company officials.