Microsoft announced that Xbox 360 has sold over 10 million units in the United States, making it the first current generation gaming console to break the ten million mark in the United States.

Globally the Xbox 360 has sold over 19 million. As you remember the Xbox 360 was first to the market in the next generation console segment already in 2005. The Nintendo Wii and the Sony PS3 came a year later. The Wii is already very close behind the Xbox 360 with 8.8m consoles sold in the United States. If Nintendo would be smarter about stocking the Wii in the States, it would have beaten the Xbox 360 to this milestone.
Microsoft also says that now twelve million Xbox LIVE gamers are registered, making Xbox Live the largest community in the connected console games sector. Xbox Live is still one of the strongest assets Microsoft has in the fight against the PS3 and Wii.
Via this Microsoft announcement. More Xbox 360 coverage.