Porsche sales fell 17.6% in the crucial North American market during the August to November period, yet the German car maker remains "moderately confident".
Plunging Cayenne sales is dragging Porsche down
A 30% drop in Porsche's Cayenne 4x4 sales cancelled out strong demand for 911 and Boxster sports cars in Germany.
Consequently, overall sales were flat, up just 0.4% to 2.05bn euros (£1.4bn; $2.7bn) compared with a year ago.
Sales may remain weak till the new Panamera four-door coupe brings about a sales revival in 2009, Porsche said.
"Until the Panamera has been launched, the focus will be on consolidation at a high level," the Stuttgart-based company said.
"Considering fluctuations in the markets, discount battles and political restraints, Porsche remains moderately confident in the 2007 year of business."
Sales of 4x4s - or sports utility vehicles - have been dropping in several key markets, on the back higher petrol prices and opposition from environmental groups.
In contrast to Porsche, its rival Mercedes has reported a 21% rise in sales in the US during last month, when compared with November 2005.
The strength in the US surpassed that seen in Europe, where Mercedes sales rose 7%.
Porsche, the world's most profitable carmaker, previously reported a near doubling in full-year profits to 1.4bn euros.
The company has been at the centre of rumours that it may be considering a takeover bid for fellow German carmaker Volkswagen.
Porsche last month said it planned to raise its stake in Europe's biggest carmaker to 29.9%, just below the threshold at which it would be required to mount a full takeover offer for the firm.
However, Porsche chief executive Wendelin Wiedeking said a takeover was "not part of our plans".