Microsoft's Xbox 360 games console goes on sale in the US on Tuesday, as stores warn customers limited supplies mean there may not be enough to go round.
Those looking to secure a new Xbox 360 may be disappointed
A similar situation is expected with its launch in the UK and Europe on 2 December, with many retailers unable to guarantee delivery by Christmas.
The item goes on sale in Japan on 10 December and rest of the world in 2006.
Microsoft has denied claims from some gamers that it is holding back output to cause a stir ahead of the launch.
Microsoft expects to sell as many as three million Xbox 360 consoles worldwide within the first 90 days of launch, and more than five million by the end of July.
But it has admitted that global supply should not catch up with demand until sometime before June.
In the UK, PC World, Amazon, and dabs.com are stating on their websites that delivery cannot be guaranteed by Christmas.
And games retailer Game said online stock will be very limited and only a proportion of online pre-orders will receive their console at launch.
"We can no longer accept new pre-orders," it said.
"We will do our best to secure more stock and these will be offered to preorder customers first."
It said that it hoped to be able to meet demand on in store orders but said it could not accept any more pre-orders and that only limited new stock was expected to come in over the Christmas holiday season.
The premium Xbox 360 with accessories has been on sale on Amazon for £279.99, but on the UK arm of auction website eBay the consoles are currently selling for between £340 and £400.
Chris Liddell, Microsoft's chief financial officer, told analysts last month that initial Xbox 360 shortages were certain, and it would replenish retail supplies more quickly than usual in the industry.
"Whereas others have shipped significant volumes for launch and then resupplied many weeks or months later, our process is to continually supply the channel on a regular basis," Mr Liddell said.
"We believe this is the better approach because it provides predictability to retailers and consumers around product availability."
Microsoft has sold more than 22 million original Xbox consoles since its launch in 2001, but it and Nintendo's GameCube remain behind Sony's dominant PlayStation 2 in market share.
Microsoft is hoping to get the jump on Sony by launching well ahead of the PlayStation 3 and Nintendo Revolution, due out next year.