President Obama has penned a letter of apology expressing “regret” over using the phrase “Polish death camps” in a ceremony earlier this week, which has drawn heavy criticism from Polish officials.

“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 wrote in a letter released by the Polish government. “I regret the error and agree that this moment is an opportunity to ensure that this and future generations know the truth.”

Earlier this week, Polish officials expressed dismay over the president’s reference to “Polish death camps” during the posthumous awarding of the Presidential Medal of Freedom, the United States’ highest civilian honor, to Jan Karski, a Polish officer who provided the Allies with underground information about the ongoing Holocaust during the Second World War.

{mosads}The remark earned front-page headlines in Polish media and a strong condemnation from Polish political leaders.

Polish Jews represented around half of the 6 million killed in the genocide, and some 300,000 were imprisoned at the Auschwitz-Birkenau death camp in Poland. 

“It’s a pity that such a dignified ceremony was overshadowed by ignorance and incompetence,” tweeted Polish Foreign Minister Radek Sikorski on Tuesday.

The White House quickly issued a statement apologizing for the president’s phrasing and amended the official transcript to include a note clarifying his remarks. But Polish officials remained outraged, arguing Obama did not understand the gravity of the situation.

“I am convinced that our American friends can today allow themselves a stronger reaction than a simple expression of regret from the White House spokesman — a reaction more inclined to eliminate once and for all these kinds of errors,” Polish Prime Minister Donald Tusk said Wednesday, according to AFP.

But the letter from President Obama received a warmer reception in Warsaw.

Polish President Bronislaw Komorowski called Obama’s letter “a very important moment in the battle for historical truth,” according to The Associated Press.