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.