LAUSANNE, Switzerland — Large US and Iranian delegations led by Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif arrived here March 15 for a crucial week of meetings. The meetings aimed at reaching a political agreement on a final nuclear accord by the end of the month, as the White House issued a new veto threat for congressional legislation it says could jeopardize a deal.

Ahead of Kerry’s arrival, lead US negotiators Undersecretary of State Wendy Sherman met with her counterparts, Iranian Deputy Foreign Ministers Abbas Araghchi and Majid Ravanchi, and their teams. US Secretary of Energy Ernest Moniz and Atomic Energy Organization of Iran (AEOI) chief Ali Akbar Salehi also held technical meetings.

Kerry, arriving from Egypt the evening of March 15, debriefed with the US team. Kerry and Zarif are due to meet March 16 starting at 8 a.m.

Congress is considering two Iran sanctions bills; one, introduced by Senate Foreign Relations Committee chairman, Bob Corker (R-Tenn.), would let Congress potentially block any Iran deal reached by the Obama administration and six world powers, by removing presidential waivers for sanctions relief for actions that Iran would take to curb its nuclear program.