With just four weeks ahead of the June 30 deadline for a final and comprehensive deal to solve the 12-year-long standoff on the Iran nuclear problem, a diplomatic source said on Saturday that there are still some gaps to be filled and the talks on Saturday ended without any big breakthrough.

　　According to a source from the Iranian delegation, the talk will be resumed next week in Vienna at the level of deputies and experts.

　　U.S., Iran hold ministerial nuclear talks ahead of final deadline

　　On Nov. 24, 2013, the world major powers and Iran reached a first-step agreement on Iran's nuclear program, which demanded Iran suspend some sensitive nuclear activities in exchange for limited sanction relief to buy time for diplomatic effort to resolve the issue.

　　Since then, the negotiators have twice missed self-imposed deadlines for a final and comprehensive accord, respectively in June and November last year, and they then set March 31 of 2015 as a new deadline for a political framework agreement and June 30 for the final deal, so as to pave the way for the final resolution of the long disputed issue.

　　On April 2 this year, they reached a framework understanding on major disputes and announced a final and comprehensive accord will be reached before June 30 this year.