Foxconn, the Taiwanese electronics giant that produces the iPhone 3G for Apple, has ramped up production to 800,000 units per week, says a source close to Apple with direct knowledge of the numbers. This is “above current full capacity” and there may be some concerns with quality control.

Apple sold just 6 million of its first generation iPhones.

Foxconn factories will be able to ramp production up significantly over time, says our source. But at current sell rates, the company is producing iPhones at a run rate of over 40 million units per year, well beyond early estimates of demand for the product of 25 million over the 3G product lifecycle.

Apple is continuing to add countries – the iPhone is available in 23 countries today, and another 50 will be added this year. We’ve heard that Foxconn was initially told to expect sales of up to 40 million units in the first year, but that those numbers are being revised upwards sharply.

About 1 billion mobile phones were sold worldwide in 2007, says Gartner (Nokia sold about 435 million of them).