US lawmakers are ramping up the pressure on Iran with less than one month to go before the June 30 deadline for a nuclear deal.

After passing legislation requiring congressional oversight of a final deal earlier this month, Congress is now headed for a showdown over whether to signal its disapproval. Doing so would curtail President Barack Obama's ability to lift sanctions and could imperil an international agreement, but is seen as unlikely to survive a presidential veto.

To inform its next steps, the Senate Foreign Relations Committee is holding a closed briefing June 2 with Energy Secretary Ernest Moniz, who was in Geneva this weekend for meetings with international negotiators, and three national laboratory directors. On June 3, the committee holds a hearing on a potential final deal's broader implications for US policy in the Middle East with former ambassador to Iraq James Jeffrey and former Assistant Secretary of State for Near East Affairs and Middle East peace envoy Martin Indyk.

In the House, the Foreign Affairs Committee holds a hearing June 2 on the Americans detained in Iran that will include the family members of Saeed Abedini, Amir Hekmati, Robert Levinson and Jason Rezaian. The hearing will be immediately followed by a vote on a sense of Congress that they be immediately released.