LAUSANNE, Switzerland, April 1 -- Chinese Foreign Minister Wang Yi hailed the nuclear talks here as an "important step" towards a comprehensive deal hoped to be reached by June 30.

All sides held comprehensive, thorough discussions on the focused issues and they have narrowed the gaps to some extent, Wang told reporters Tuesday night.

A new round of Iranian nuclear talks resumed since March 26 and all foreign ministers from P5+1 countries and Iran joined the talks as from March 29 to further diminish differences.

"This round of minister-level meeting is beneficial," he said. "It is an important step forward to achieving the final comprehensive agreement."

Wang told reporters that the remaining key issues were linked to each other, but that all parties must think creatively to find a common solution.

The Chinese top negotiator raised a four-point proposal for the next phase of nuclear talks, which was giving political guidance to the negotiation, narrowing down the differences, adhering to a step-by-step approach and reciprocity, and striving for a package solution.

He pointed out that resolving the Iranian nuclear issue would involve a process and all sides must advance step by step on the basis of reciprocity.

The foreign minister called for all parties to shoulder due responsibility and obligation.

"No agreement is possible without accommodating the core concerns of the various parties," he said, adding it is important to give play to the role of the UN Security Council.