WASHINGTON — Pushing back hard, President Obama forcefully defended the 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 that negotiators will soon begin to work out.

DEAL ON MONITORING, SANCTIONS

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 U.S., Britain, France, Russia, China and Germany – is to temporarily halt parts of Tehran’s disputed nuclear program and allow for more intrusive international monitoring of Iran’s facilities. 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.

The groundwork for the accord was laid during four clandestine meetings between U.S. and Iranian officials throughout the summer and fall. Details of the secret talks were confirmed to The Associated Press by three senior administration officials.

POTENTIAL FOR HISTORIC AGREEMENT

The U.S. and its allies contend Iran is seeking to produce a nuclear bomb – of particular concern to Israel, which fears an attack – while Tehran insists it is merely pursuing a peaceful nuclear program for energy and medical purposes.

Obama made sure 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 … I’ve done what I’ve said.”

The temporary accord is historic in its own right, marking the most substantial agreement between Iran and the West in more than three decades. The consequences of a permanent deal could be far more significant, lowering the prospects of a nuclear arms race in the volatile Middle East and perhaps opening the door to wider relations between the U.S. and Iran, which broke off diplomatic ties after the 1979 Islamic revolution.