World

After week of nuclear talks with Iran, Kerry cites 'substantial progress' but says gaps remain

  • U.S. Secretary of State John Kerry speaks during a  news conference after bilateral meetings with Iranian Foreign Minister Mohammad Javad Zarif  about  Iran's nuclear program ,  in Lausanne, Switzerland, at the Olympic Museum, Saturday, March 21, 2015.  (AP Photo/Keystone,Laurent Gillieron)

    U.S. Secretary of State John Kerry speaks during a news conference after bilateral meetings with Iranian Foreign Minister Mohammad Javad Zarif about Iran's nuclear program , in Lausanne, Switzerland, at the Olympic Museum, Saturday, March 21, 2015. (AP Photo/Keystone,Laurent Gillieron)  (The Associated Press)

  • U.S. Secretary of State John Kerry, right, is greeted by British Foreign Secretary Philip Hammond in London, England, Saturday, March 21, 2015, for a meeting about the recently concluded round of negotiations with Iran over Iran's nuclear program.   (AP Photo/Brian Snyder, Pool)

    U.S. Secretary of State John Kerry, right, is greeted by British Foreign Secretary Philip Hammond in London, England, Saturday, March 21, 2015, for a meeting about the recently concluded round of negotiations with Iran over Iran's nuclear program. (AP Photo/Brian Snyder, Pool)  (The Associated Press)

  • U.S. Secretary of State John Kerry (2nd left) and German Foreign Minister Frank Walter Steinmeier (Right) attend a meeting about the recently concluded round of negotiations with Iran over Iran's nuclear program, in London, England, Saturday, March 21, 2015. (AP Photos / Brian Snyder, pool)

    U.S. Secretary of State John Kerry (2nd left) and German Foreign Minister Frank Walter Steinmeier (Right) attend a meeting about the recently concluded round of negotiations with Iran over Iran's nuclear program, in London, England, Saturday, March 21, 2015. (AP Photos / Brian Snyder, pool)  (The Associated Press)

U.S. Secretary of State John Kerry says "substantial progress" has been made toward ensuring that Iran's nuclear program will not lead to weapons development.

But he says important gaps still stand in the way of an agreement.

Speaking after a week of nuclear talks with Iran, Kerry said Saturday that the U.S. wasn't rushing for an agreement even as a March 31 deadline looms for a framework agreement.

He said fundamental decisions needed to be made and stressed that world powers and Iran have an opportunity right now for a diplomatic solution.

Kerry was departing later Saturday for London to meet with European allies, before returning to Washington.

Talks with Iran resume next week.