COEUR d'ALENE - GOP presidential candidate Newt Gingrich said Thursday a U.S. apology to Afghan authorities for burned Qurans on a military base was "astonishing" and undeserved.

Gingrich lashed out at President Barack Obama for the formal apology after copies of the Muslim holy book were found burned in a garbage pit on a U.S. air field earlier in the week

Obama's apology was announced Thursday morning. A few hours later, news organizations reported that an Afghan soldier had killed two U.S. troops and wounded others in retaliation for the Quran burning.

Campaigning in Washington state, Gingrich said Afghan President Hamid Karzi owes the U.S. an apology for the shootings.

"There seems to be nothing that radical Islamists can do to get Barack Obama's attention in a negative way and he is consistently apologizing to people who do not deserve the apology of the president of the United States period," Gingrich said.

"And, candidly, if Hamid Karzai, the president of Afghanistan, doesn't feel like apologizing then we should say good bye and good luck, we don't need to be here risking our lives and wasting our money on somebody who doesn't care."

Even before Gingrich's comments, White House spokesman Jay Carney sought to counter any criticism of the president's apology.

"It is wholly appropriate, given the sensitivities to this issue, the understandable sensitivities," Carney told reporters traveling to Miami with the president on Air Force One. "His primary concern as commander in chief is the safety of the American men and women in Afghanistan, of our military and civilian personnel there. And it was absolutely the right thing to do."

Later Thursday, Gingrich continued his criticism of Obama's foreign policy during a rally in the town of Coeur d'Alene in North Idaho, a stop in one of the 10 states that votes on March 6. He was spending Friday in Washington state, which holds caucuses a week from Saturday.

"This president has gone so far at appeasing radical Islamists that he is failing in his duty as commander in chief," Gingrich said.

Associated Press writers Julie Pace and Shannon Dininny contributed to this report.