LONDON (AFP) - Downing Street moved swiftly to play down an apparent admission by British Prime Minister Tony Blair that the invasion of Iraq had been a "disaster," labelling his comments a "slip of the tongue." In an interview Friday on Al-Jazeera's new English-language channel, broadcaster Sir David Frost suggested that the 2003 US-led and British-backed invasion had "so far been pretty much of a disaster." "It has," Blair replied, before adding quickly: "But you see, what I say to people is why is it difficult in Iraq? It's not difficult because of some accident in planning. "It's difficult because...