Parties in the new round of talks on Iran's nuclear program have showed strong political will and pragmatic attitude, China's representative Wang Qun said on Friday.

This is the fifth round of negotiations since the P5+1, namely the United States, China, Russia, France, Britain, plus Germany, and Iran reached a decision on extension of negotiations on a comprehensive deal in November 2014.

Wang told Xinhua that the week-long talks, held in Lausanne, Switzerland and suspended on Friday, made important advancement, though a plenary session of P5+1 countries and Iran failed to take place.

The parties held intensive multilateral and bilateral meetings, displaying strong political will, substantive attitude, as well as innovative thoughts and ideas in the crucial round of negotiations at a critical stage, Wang said.

"Negotiations are like rowing upstream, not to advance means backing off," Wang said, urging all sides to move forward to forge a final agreement with firmer political will.

"Without political determination, it is impossible to achieve a mutual-beneficial compulsory agreement," stressed Wang, who led the Chinese delegation and joined the negotiations from Wednesday.

The remaining gap is complex, Wang noted, adding that two categories of issues are to be settled: one is how to guarantee Iran's rights to peaceful use of nuclear energy, and the other is how to deal with the non-proliferation concerns related to Iran's nuclear program.

He said China, which has played a constructive role in the nuclear negotiations, proposed in the latest round of negotiations a series of plans and ideas to bridge gaps.

China would like to work with other parties to promote an early clinching of a comprehensive political agreement, he added.

The nuclear negotiations will be resumed in Lausanne later next week.