VIENNA, March 18 -- Key elements of a comprehensive accord will be the main topic during the new round of nuclear talks between six world powers and Iran, the head of a Chinese delegation said Tuesday.

"The focal point of the talks is about what elements should be included in the comprehensive deal," Wang Qun, China's chief negotiator, told Xinhua ahead of the talks scheduled for Tuesday to Thursday.

Based on the progress made in the last round of talks between Iran and the P5+1 group (Britain, China, France, Russia, the United Stated plus Germany), this week's negotiations were expected to yield more substantive results for the comprehensive agreement, he said.

"There will be specific issues in this round of talks," Wang said, adding, although the upcoming talks seemed tougher than the last round, he believed all sides had a sincere attitude.

Last November, the P5+1 group and Iran reached an interim deal on Iran's nuclear program in Geneva, which came into effect on Jan. 20.

Under the deal, Iran suspended the most sensitive parts of its nuclear activities in exchange for partial relief of the West's sanctions. The parties involved are also striving to clinch a comprehensive accord over the decade-long nuclear standoff.