Polish President Bronislaw Komorowski, with permission from the White House, posted the letter on his Web site, ABC News reported. Obama's gaffe occurred while he was honoring Jan Karski -- a Polish national who reported on the destruction of the Warsaw Ghetto and the death camps and later moved to the United States -- with a posthumous Medal of Freedom.
"In referring to 'a Polish death camp' rather than 'a Nazi death camp in German-occupied Poland,' I inadvertently used a phrase that has caused many Poles anguish over the years and that Poland has rightly campaigned to eliminate from public discourse around the world," Obama said.
Komorowski accepted the apology.
"With this letter Poland has gained an important ally in its battle against the misleading, wrongful and painful term 'Polish death camps,'" he wrote in response.
In his letter, Obama paid tribute to the Polish resistance during World War II.
"The killing centers at Auschwitz-Birkenau, Belzec, Treblinka and elsewhere in occupied Poland were built and operated by the Nazi regime," he said. "In contrast, many Poles risked their lives -- and gave their lives -- to save Jews from the Holocaust."