it was their first meeting since world powers and iran sealed a framework deal on april 2 that would limit iran 's ability to build a nuclear weapon .
final agreement hinges timing of sanctions relief - something both sides have said they wo n't budge on .
obama administration is also engaged in an aggressive effort to sell the emerging deal to skeptical lawmakers and constituencies in washington .
gop presidential candidates are lining up to oppose any deal with a government the u.s. considers the leading state sponsor of terrorism .
house speaker john boehner has acknowledged that his party does n't command enough votes to override a veto of any resolution , though .