The letter sent by 47 Republican senators to Iranian negotiators claims that the nuclear deal being worked on with the U.S. could be scrapped by Congress. It has left the White House scrambling to keep the negotiations on track.
The Iranian foreign minister called the letter unprecedented, and says it raises the possibility that the United States is untrustworthy as a negotiating partner.
Meanwhile, congressional Democrats and the Obama administration are blasting the Republicans for interfering in the talks. Here & Now's Robin Young gets the latest from NPR congressional correspondent Ailsa Chang.
This segment aired on March 10, 2015.