The BBC reports that high street retailers are struggling to keep up with demand for the console, which has been in short supply for months.
Nintendo said it was "doing everything possible" to keep up with demand and has promised as an extra 3.5 million consoles globally, in time for the Christmas rush.
Despite recent dips in sales in Japan, the console is still selling strongly across the world. In April Nintendo estimated a yearly shipment of 14 million units, but that has now been raised to 17.5.
"The demand for Wii hardware globally has been unprecedented and higher than Nintendo could ever have anticipated", said a spokesperson for the company. Stock shortages could last into the new year.
In America, shortages of the Wii have been credited as one reason the PlayStation 3 has seen its sales figures double recently, that, and the new cheaper model and price cut.