President Obama today defended the Iranian nuclear deal against criticism from skeptics at home and abroad, arguing that "we cannot close the door on diplomacy."

"We cannot rule out peaceful solutions to the world's problems. We cannot commit ourselves to an endless cycle of conflict. And tough talk and bluster may be the easy thing to do politically, but it's not the right thing for our security," the president said at an immigration event in San Francisco.

Obama went on to describe the pact as an example of his administration's "clear eyed and principled diplomacy" with its adversaries.

"We're going to continue our diplomacy with the goal of achieving a comprehensive solution that deals with the threat of Iran's nuclear program once and for all," he said. "And if Iran seizes this opportunity and chooses to join the global community, then we can begin to chip away at the mistrust that's existed for many, many years between our two nations."

While admitting that "huge challenges remain," Obama - invoking former President Kennedy's famous words - said it's important to "let us never negotiate out of fear, but let us never fear to negotiate.'"

"I believe that," he said.