Barack Obama says nuke deal offers chance of 'new direction' in Iran ties

Washington: US President Barack Obama on Tuesday lauded a landmark nuclear agreement with Iran as a vindication of diplomacy, and a step that offered a chance at a "new direction" in vexed relations with Tehran.

Obama said the deal -- which would curb Iran's nuclear program in return for sanctions relief -- cut off "every pathway" to an Iranian atomic weapon.

"Today, because America negotiated from a position of strength and principle, we have stopped the spread of nuclear weapons in this region," he said in a White House address.

Describing a "difficult history" between Iran and the United States that "cannot be ignored," Obama said the diplomatic victory also showed "it is possible to change."

"This deal offers an opportunity to move in a new direction. We should seize it," he said.

Relations between the US and Iran were smashed amid the tumult of the 1979 Islamic Revolution and the subsequent seizing of hostages at the US embassy in Tehran.

Obama came to office vowing to give diplomacy a chance -- a marked shift from his predecessor who rejected a similar deal negotiated by European countries.

Firmly tethering his presidential legacy to Tuesday's deal, Obama warned it was "irresponsible" to walk away from the agreement and vowed to veto any effort in the Republican-controlled Congress to block it.

Read: Timeline of Iran's 13-year nuclear standoff

"This deal demonstrates that American diplomacy can bring real and meaningful change," he said.

But, he warned, if Iran steps back from measures agreed in the lengthy agreement, all sanctions "will snap back into place."

Diplomats have long warned the deal will not bring smooth waters.

Read: John and Javad, the odd couple who struck the Iran deal

Even if Iran stands by agreements to allow intrusive monitoring, its security services continue to back groups throughout the Middle East that Washington has linked to terror attacks.

Obama noted that differences between the two countries were "real," adding that the deal was based on verification, not trust.

Analysts have also warned that Iran's leaders may need to toughen anti-American rhetoric to ensure the backing of regime hardliners who were angered at the prospect of a deal with a power they view as the "Great Satan."