Oil industry executives on Tuesday sharply criticized President Barack Obama?s six-month ban on deepwater drilling, saying the world did not have enough other sources of oil to eliminate using deepsea rigs. The massive oil slick in the Gulf of Mexico and the moratorium imposed by Obama dominated discussions at the World National Oil Companies Congress in the British capital, and a BP executive standing in for embattled BP CEO Tony Hayward was heckled by protesters. Transocean president and CEO Steven Newman, owner of the destroyed Deepwater Horizon rig that has spewed millions of gallons of oil into the Gulf, said Obama?s ban, which is currently being reviewed by a US federal judge, was unnecessary.