The United States says the six countries negotiating with Iran over its nuclear programme would consider a limited pullback of sanctions in exchange for clear evidence Teheran is taking steps to stop the programme from advancing.
Talks are being held in Geneva, seeking to build on a diplomatic opening from Tehran after the election of President Hassan Rouhani, a relative moderate, in June.
The West fears Tehran's nuclear programme may be aimed at developing a nuclear weapons capability.
Iran met negotiators from the United States, Britain, France, Germany, Russia, and China for the first day in Geneva on Thursday.
If Iran fails to show progress on its nuclear programme, the White House says the moderate sanctions relief being suggested could be reversed and stiffer sanctions could be imposed.
