British Prime Minister Tony Blair is announcing today that he will resign after 10 years of leading Britain's government, a Labour party official said. "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." According to the Associated Press, Blair was traveling to his northern England parliamentary district to formally announce his plans. He met earlier with Cabinet members, who left No. 10 Downing Street without answering questions shouted by reporters. Blair would leave office in late June or early July, depending on how quickly his party elects a successor - almost certain to be Treasury Chief Gordon Brown. Burton said Blair would continue to represent Sedgefield in Parliament for the time being, but could not confirm whether he would stand down before the next national election expected in 2009 or 2010. Blair's resignation is an announcement that his Labour Party, and the nation, have been expecting for nearly three years, ever since the prime minister said in 2004 that his third term -- SPA