Due to stronger than expected US sales, Apple is delaying the iPad's international release until the end of May.

The company has already sold 500,000 wi-fi only iPads in the US and expects that number to increase drastically when the 3G model hits shelves.

In a statement Apple said: “Although we have delivered more than 500,000 iPads during its first week, demand is far higher than we predicted and will likely continue to exceed our supply over the next several weeks as more people see and touch the iPad.”

The statement also said: “Faced with this surprisingly strong US demand, we have made the difficult decision to postpone the international launch of iPad by one month, until the end of May.”

Apple will reveal international pricing and start taking online pre-orders on May 10th, but the actual devices won’t ship until the end of the month.

Apple originally announced that the first countries to receive the iPad would be Australia, Canada, France, Germany, Italy, Japan, Spain, Switzerland and the UK. There’s no official word yet on when the iPad will be released in New Zealand, though unlike the original iPhone, the iPad offers the wi-fi only version and the 3G model doesn’t require a US contract, and iPads have been popping up in a number of countries where the iPad hasn’t officially been released.