President Obama spoke in defense of the nuclear deal with Iran that was announced on Tuesday, which has been criticized by some in Washington and abroad.  WASHINGTON — President Obama eagerly took on critics of the Iran nuclear deal on Wednesday, inviting question after question on an agreement he suggested that many of his political adversaries had not even read.  Mr. Obama used a formal East Room news conference to begin what White House officials said would be an aggressive effort by the president and his top advisers over the next 60 days to combat critics in both parties and to sell the Iran deal to members of Congress, the public and allies in the region.  While Mr. Obama is expected to win enough votes to sustain a veto of any legislation rejecting the deal, his goal over the next two months is to persuade enough Democrats to support the accord so that he can paint opponents as driven by politics rather than diplomacy.  He appeared to relish the fight as he adopted a bring-it-on demeanor and invited reporters to ask him more about the deal.  “Have we exhausted Iran questions here?” he asked at one point. “I think there’s a helicopter that’s coming, but I really am enjoying this Iran debate.”  He then disregarded a prepared list of reporters to call on and, like a boxer beckoning someone to throw a punch, asked for more questions on Iran from the room.  “I just want to make sure that we’re not leaving any stones unturned here,” he said. As Mr. Obama spoke, his critics continued to hammer against it. Senator Tom Cotton, Republican of Arkansas, one of the deal’s most ardent critics, said it represented a “nuclear agreement with an outlaw regime” and predicted that “the American people will repudiate this deal and Congress will kill the deal with a veto-proof majority.”  Most American Jewish groups were also mobilizing strongly against the accord. The pro-Israel lobby Aipac denounced the deal as one that “would facilitate rather than prevent Iran from obtaining a nuclear weapon and would further entrench and empower the leading state sponsor of terror.”  “Proponents of the proposed agreement will argue that the only alternative to this agreement is military conflict,” Aipac said in a statement calling on Congress to reject the deal and to insist on a better one. “In fact, the reverse is true. A bad agreement such as this will invite instability and nuclear proliferation. It will embolden Iran and may encourage regional conflict.”  The Orthodox Union and the Rabbinical Council of America issued a joint statement saying they had scrutinized the pact and found it “seriously wanting,” calling the inspection regime insufficient and the billions of dollars in sanctions for relief for Iran unacceptable. They said they would be mobilizing rabbis and synagogues across the nation to oppose the measure and urge lawmakers to reject it.  In the past, Mr. Obama has often appeared defensive or defeated as he faced questions about the failure of his health care website or other foreign policy challenges. But in this case he avidly raised and dismissed many objections without even being asked. For those who argue that the administration could have forced the Iranians to agree to a deal that would leave Iran with no nuclear capacity, “there is nobody who thinks that Iran would or could ever accept that,” he said.  And for those who say that the current sanctions on Iran are better than the negotiated deal, Mr. Obama said that without a diplomatic agreement the present sanctions regime would break down.  “Without a deal, the international sanctions regime will unravel with little ability to reimpose them,” he said.  A guide to help you navigate the talks between global powers and Tehran.  The president did concede that the people of Israel — where the deal has been met with hostility and skepticism from across the political spectrum — have “legitimate concerns” about whether Iran emerges with a greater ability to back terrorism and disrupt its neighbors.  “You have a large country, with a significant military, that has proclaimed that Israel shouldn’t exist, that has denied the Holocaust, that has financed Hezbollah,” Mr. Obama said, speaking of Iran. “There are very good reasons why Israelis are nervous about Iran’s position in the world, generally.”  But Mr. Obama insisted that “those threats are compounded if Iran gets a nuclear weapon.”  With a better deal impossible, Mr. Obama said that the only viable alternative to the negotiated settlement his administration had presented was war. And he challenged critics of the deal to acknowledge that what they really wanted was a military solution.  “And if the alternative is that we should bring Iran to heel through military force, then those critics should say so, and that will be an honest debate,” Mr. Obama said.  Mr. Obama said he hoped the agreement would pave the way to a more constructive relationship with Iran. But he rejected the idea that the deal deserved to be opposed because it failed to address Iran’s support for terrorism or its destabilizing activities in the Middle East.  “My hope is that building on this deal, we can continue to have conversations with Iran that incentivizes them to behave differently in the region, to be less aggressive, less hostile, more cooperative,” Mr. Obama said. “But we’re not counting on it.”  The agreement, he said, “solves one particular problem,” which is the risk of Iran developing a nuclear weapon.  He finally said he had to go, but promised to return to the subject of the Iran deal.  “I think we’ve hit the big themes, but I — but I promise you I will — I will address this again, all right?” he said. “I suspect this is not the last that we’ve heard of this debate.”  Julie Hirschfeld Davis contributed reporting.  A version of this article appears in print on July 16, 2015, on page A11 of the New York edition with the headline: Obama Begins 60-Day Campaign to Win Over Skeptics at Home and Abroad. Order Reprints| Today's Paper|Subscribe
“If we don’t choose wisely,” the president said, “I believe future generations will judge us harshly, for letting this moment slip away.”