WASHINGTON – President Obama forcefully defended Sunday's temporary agreement to freeze Iran's disputed nuclear program on Monday, declaring that the United States "cannot close the door on diplomacy."

The president's remarks followed skepticism of the historic accord expressed by some U.S. allies abroad as well as by members of Congress at home, including fellow Democrats. Israeli Prime Minister Benjamin Netanyahu, one of the fiercest opponents of the six-month deal, called it a "historic mistake" and announced he would be dispatching a top envoy to Washington to try to toughen the final agreement negotiators will soon begin hammering out.

Obama, without naming names, swiped at those who have questioned the wisdom of engaging with Iran.

"Tough talk and bluster may be the easy thing to do politically, but it's not the right thing to do for our security," he said during an event in San Francisco.

The weekend agreement between Iran and six world powers — the United States, Britain, France, Russia, China and Germany — suspends parts of Tehran's nuclear program and allows for more intrusive international monitoring. In exchange, Iran gains some modest relief from stiff economic sanctions and a pledge from Obama that no new penalties will be levied during the six months.

Despite the fanfare surrounding the agreement, administration officials say key technical details on the inspections and sanctions relief must still be worked out. Those talks will tackle the most difficult issues, including whether Tehran will be allowed to enrich uranium at a low level.

Iran insists it has a right to enrich uranium for peaceful purposes, and many nuclear analysts say a final deal will almost certainly leave Iran with some right to enrich. However, that's sure to spark more discord with Israel and many lawmakers who insist Tehran be stripped of all enrichment capabilities. British Foreign Secretary William Hague said he expects the deal to be fully implemented by the end of January.

European Union officials say their sanctions could be eased as soon as December. Those restrictions affect numerous areas including trade in petrochemicals, gold and other precious metals, financial transfers to purchase food and medicine, and the ability of third countries to use E.U.-based firms to insure shipments of Iranian oil again.

Even with the criticism, for Obama the sudden shift to foreign policy presents an opportunity to steady his flailing second term and take some attention off the domestic troubles that have plagued the White House in recent weeks, especially the rollout of his health care law. He made sure on Monday to draw a connection between the nuclear pact and his long-declared willingness to negotiate directly with Iran.

"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," he said. "As president and as commander in chief, I've done what I've said."

Obama and his advisers know the nuclear negotiations are rife with risk. If he has miscalculated Iran's intentions, it will vindicate critics who say his willingness to negotiate with Tehran is naive and could hasten the Islamic republic's march toward a nuclear weapon. Obama also runs the risk of exacerbating tensions with key Middle Eastern allies.

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