"Working (on an agreement) is difficult and time-taking ... and in case we cannot come to a conclusion today (Saturday), the talks will resume in seven to 10 days," he said.
"We are ready to work together (with the other party) on a proper plan in which the rights of our nation is addressed ... ( but) as we have said earlier we will not allow anybody to develop a plan for us," Zarif said.
Iran and the P5+1 countries -- including Britain, China, France, Russia and the US plus Germany -- began crucial talks on Iran's nuclear issue in Geneva Thursday.
Iran insists on uranium enrichment activities within the country and urges the powers to lift sanctions which have hit its oil industry and financial system.
According to the media, the West is at odds with Iran and calls on the country to halt high-grade uranium enrichment, to ship out or oxidise the stockpile of its 20-percent enriched uranium and to stop working on its heavy water project.
Iran insists on uranium enrichment activities within the country.
Earlier, Zarif had pointed out the existing differences among the world powers over a deal on Iran's nuclear issue in the ongoing talks.
"It is unclear whether we will reach an agreement on a draft of the joint statement," said Zarif. "There are agreements on some of the topics and differences on others."
Also, "there are different views (over some aspects of the agreement) among the P5+1 countries," reported Xinhua citing him without elaboration.
"We need our concerns to be addressed in the agreement as well," and it needs time to work on the final draft, said Zarif, adding that therefore, if the draft is not concluded, talks could continue in the coming days.