"Our enemies respect no freedom of religion. Al Qaeda's cause is not Islam -- it is a gross distortion of Islam," he said. "These are not religious leaders -- these are terrorists who murder innocent men, women and children. In fact, al Qaeda has killed more Muslims than people of any other religion -- and that list of victims includes innocent Muslims who were killed on 9/11."
While many welcome the president's support, his speech runs counter to the opinions held by a majority of Americans.
A CNN/Opinion Research Corp. poll released this week found that nearly 70 percent of American opposed the plan while just 29 percent approved.
The Islamic center has won approval from the local planning board, but still faces legal and political challenges that may prevent its completion.
ABC News' Sunlen Miller and The Associated Press contributed to this report.