Obama:Violence affects hope for dialogue with Iran

Their bravery in the face of brutality is a testament to their enduring pursuit of justice. The violence perpetrated against them is outrageous.

"Iran's possession of nuclear weapons will trigger an arms race in the Middle East that would be bad ... for the security of the entire region," Obama said.

"So even as we clearly speak out in a unified voice in opposition to the violence that's taken place in Iran, we also have to be steady in recognizing that the prospect of Iran with a nuclear weapon is a big problem."