The letter – which echoes a similar one sent by senators in February – will among other things take note of testimony given by Secretary of State John Kerry declaring that the administration “would be obligated… under the law” to come to Congress in order to unwind sanctions:

  The letter states: “When asked if your Administration would come to Congress to secure legislative relief of sanctions in a final agreement with Iran, in a recent Congressional hearing, Secretary of State John Kerry responded: ‘(w)ell, of course. We would be obligated to under the law.’ He added that ‘what we do will have to pass muster with Congress.’ We strongly agree with the Secretary’s assessment, and believe the final agreement must verifiably ensure that Iran is denied an undetectable nuclear weapons breakout capability.”

The Hill picked out portions of the letter that emphasized that “most U.S. sanctions are intertwined with Iran’s other actions… includ[ing] its ballistic missile program, its nonconventional weapons program and its support for international terrorism” and that “this detail… will require ‘extensive engagement’ and approval from Congress.”

The White House is thought to have explored options under which President Obama could unilaterally lift sanctions on Iran in the context of an agreement with Tehran:

  Congressional insiders say that the White House is worried Congress will exert oversight of the deal and demand tougher nuclear restrictions on Tehran in exchange for sanctions relief.

  Top White House aides have been “talking about ways to do that [lift sanctions] without Congress and we have no idea yet what that means,” said one senior congressional aide who works on sanctions. “They’re looking for a way to lift them by fiat, overrule U.S. law, drive over the sanctions, and declare that they are lifted.”

 There is a strain of journalism that has emerged in recent weeks justifying such moves – and at least one report [PDF] that envisioned a complicated process by which some sanctions expired, some sanctions were vetoed, and some sanctions were left unenforced – but even D.C. lobbies accused of peddling regime propaganda have conceded that such scenarios are unworkable.

 A few weeks ago a bipartisan group of veteran diplomats and analysts – Eric Edelman, Dennis Ross, and Ray Takeyh, respectively a former undersecretary of defense during the George W. Bush administration, a special assistant to President Obama, and a senior fellow at the Council on Foreign Relations – made the same point.