US President Barack Obama has expressed “regret” at what he called his inadvertent use of the erroneous term “Polish death camp”, in a personal letter to his Polish counterpart made public Friday. “I regret the error and agree that this moment is an opportunity to ensure that this and future generations know the truth,” Obama wrote to Polish President Bronislaw Komorowski in the letter dated May 31. Obama on Tuesday labeled a World War II Nazi German facility used to process Jews for extermination a “Polish death camp.” The White House later said the president misspoke and expressed “regret”. Polish leaders termed the error “hurtful” and said it required more than a mere expression of regret.