U.S. says it is too soon to say if Iran has returned to nuclear talks with a more constructive approach

FILE PHOTO: A staff member removes the Iranian flag from the stage after a group picture with foreign ministers and representatives of the U.S., Iran, China, Russia, Britain, Germany, France and the European Union during the Iran nuclear talks at the Vienna International Center in Vienna, Austria July 14, 2015. REUTERS/Carlos Barria/File Photo

WASHINGTON (Reuters) - It is too soon to say whether Iran has returned to nuclear talks with a more constructive approach, the U.S. State Department said on Monday, after Iran's top nuclear negotiator said progress had been made.

State Department deputy spokeswoman Jalina Porter made the comment during a briefing call with reporters.