As the US Congress begins its two-month review of the nuclear agreement with Iran, lawmakers skeptical about the deal are mounting pressure on President Obama’s administration to make more information public.

U.S Secretary of State, John Kerry; Treasury Secretary, Jack Lew and Energy Secretary, Ernest Moniz, are set to testify before the Senate Foreign Relations Committee, in what will be the first of such public appearance by the cabinet officials since the deal was announced on July 14.

They had earlier briefed the entire Senate and House of Representatives in separate closed-door sessions on Wednesday and administration officials have held a series of private telephone conversations and meetings with lawmakers.

The demands by the lawmakers include more information about the timing of sanction reliefs and the ability to “snap back” sanctions if Iran cheats.

The Republican Chairman of the Foreign Relations Committee, Senator Bob Corker said, “We have leverage, but in nine months, they will have their cash and all the sanctions will be relieved. People will be in there signing contracts, and then the leverage sort of shifts to them.”