HONOLULU, Hawaii (AFP) - The United States on Wednesday marks the 70th anniversary of the attack on Pearl Harbour with memorial services, lowered flags and silence at the moment the history-changing assault began. Ceremonies were scheduled from Pearl Harbour in Hawaii to Washington DC on the US East Coast to remember the 2,400 Americans who died on December 7, 1941 when Japan launched a devastating surprise offensive on the US Pacific Fleet. Obama called for the Stars and Stripes to be flown at half mast on federal buildings across the country.