London - Former British Prime Minister Tony Blair said he was "desperately sorry" for deaths in the Iraq war but insisted the controversial 2003 invasion was right in his memoirs published Wednesday.

Entitled "A Journey", the book is Blair's account of his decade in Downing Street from 1997 to 2007 and also features an unprecedented, stinging attack on his successor Gordon Brown, whose premiership he brands a disaster.

However, it is Iraq, arguably the defining event of Blair's decade in power -- which is at the book's heart.

Blair said he was "desperately sorry" over casualties on all sides -- British soldiers, their allies, Iraqi civilians, diplomats and casualties such as murdered hostages -- and suggested he had shed tears over the loss of life.

And in a BBC interview being broadcast Wednesday to publicize the book, Blair added that the international community should be prepared to consider taking military action against Iran if it develops a nuclear weapon.