VIENNA, July 14 (Xinhua) -- U.S. Secretary of State John Kerry would continue to press his Iranian counterpart Javad Zarif to make progress in nuclear talks in a second bilateral meeting on Monday, according to a senior U.S. official.
Kerry would "gauge Iran's willingness" and urge Zarif to make "critical choices" over a uranium enrichment program, after the two held discussions in Vienna Sunday with no major breakthrough.
The two top diplomats talked for two hours on Sunday on the sidelines of a meeting between Iran and the five permanent members of the UN Security Council -- the United States, Britain, France, Russia and China -- plus Germany (P5+1 group).
Kerry said there were still substantial gaps between Iran over uranium enrichment, as a July 20 deadline for a comprehensive deal is looming.
But Zarif, after the meeting with Kerry, said the talks had "made some important headway" and expressed his willingness to continue the talks with his U.S. counterpart the following day.
Iran insists that its uranium enrichment is for peaceful purpose and urges an end to international sanctions, while the United States and other powers suspect it is seeking nuclear weapons.
An interim deal was reached last year and the deadline of July 20 was set for a final and comprehensive agreement.
Since the significant gaps are not bridged in the talks, and time is running short, experts believe that the negotiation could probably need more time to reach a final deal.