(Photo Credit: ABC News)

Former President George W. Bush will make no public statement on the developing crisis in Iraq, his spokesman said today.

"President Bush has vowed not to criticize his successor and does not have a comment," Freddy Ford told ABC News in a statement.

Bush spent years engaged in the war in Iraq, while President Obama campaigned against it and eventually pulled out U.S. troops. Some Republicans have blamed Obama for the violence because they believe the troop pullout has left a security vacuum.

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President Obama today ruled out sending U.S. troops "back into combat" in Iraq despite the threat from a surging army of Islamic militants.

But as several cities in the once U.S.-occupied nation fall under the flags of the Islamic State of Iraq and Syria, or ISIS, Obama told reporters his National Security Council was still considering options.

"I'll be reviewing those options in the days ahead," Obama said on the White House South Lawn. "I do want to be clear, though. This is not solely, or even primarily, a military challenge."