LONDON - Prime Minister Tony Blair is announcing Thursday that he will resign after 10 years of leading Britain's government, a Labour party official said.

British Prime Minister Tony Blair arrives back at 10 Downing Street after Prime Minister's Questions at the House of Common, London, Wednesday, May 9, 2007. [AP]

"There are a mixture of emotions today. There's disappointment and sadness that we are losing the prime minister after 10 years," said John Burton, Blair's political representative in the constituency. "But there's joy, happiness and thanks for what has been achieved."

Blair was traveling to his northern England parliamentary district to formally announce his plans following a brief meeting with the Cabinet in London.