Nuclear negotiations between the United States and Iran resumed Thursday in Switzerland with a deadline for an agreement just days away - and fighting in Yemen hanging over the talks.
U.S. Secretary of State John Kerry said before his meeting with Iranian Foreign Minister Mohammed Javad Zarif that the alternative to a deal is letting Iran expand its nuclear program "full speed ahead."
He pointed out that those opposed to the talks have yet to propose a "viable, realistic alternative."
Iranian President Hassan Rouhani's office said the president told British Prime Minister David Cameron by telephone Thursday that Iran is "acting in the national and international interest and we should not lose this exceptional opportunity."
The State Department says Kerry and Zarif briefly talked about Yemen, but gave no details. The United States supports Gulf state airstrikes against Iranian-backed Houthi rebels in Yemen.
The U.S. and its P5 Plus 1 partners - Britain, China, France, Russia, and Germany -- have a March 31 deadline for a framework deal with Iran. The deadline has already been extended twice and there is little support for doing it again.
The six partners want Iran to curb its uranium enrichment program to prevent it from being able to build a nuclear weapon. In exchange, devastating economic sanctions on Iran would be lifted.
Iran denies wanting to build nuclear bombs and insists its nuclear program is for peaceful, civilian purposes.