The U.S. president has defended his administration’s efforts in forging an agreement with Iran, stressing that the United States “cannot close the door on diplomacy.”

The agreement to put a freeze on the imposition of new sanctions on Iran has been heavily criticized by some U.S. senators as well as Israel.

Speaking in San Francisco, Barack Obama said: “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.”

The U.S. president added: "When I first ran for president, I said it was time for a new era of American leadership in the world, one that turned the page on a decade of war and began a new era of engagement with the world. As president and as commander in chief, I've done what I've said.”

The preliminary deal has been hailed as a welcome development by the Iranian delegation as well as the other 5+1 countries.

The negotiations are set to resume next month or early next year with the objective of reaching a final deal.