Iran nuclear talks resume in 'positive' spirit NEW: Foreign Minister Javad Zarif says Iran's plan has been "welcomed as a new approach" Iranian state media: Iran and Britain plan to introduce nonresident diplomats soon "For the first time, we had very detailed technical discussions," U.S. official says of talks Geneva, Switzerland (CNN) -- Iran and six world powers entered a second day of talks Wednesday over Tehran's nuclear ambitions, after what appeared to be a positive opening exchange. Both sides struck a tone of cautious optimism after the first day of negotiations in Geneva Iranian Foreign Minister Javad Zarif, who's leading the Iranian delegation, said in a Facebook post Wednesday that their proposal outlined "a new view which emphasizes the need for pursuing a common goal by all players" and identified areas that must be agreed upon. This framework was welcomed as a new approach by the heads of the delegations. Of course we would like to see a new approach by the 5+1 as well," he said. The meetings will continue for several weeks in Geneva, Zarif said. He said progress will take time and warned that any leaks from the talks will undermine trust. "Discussions and reaching a solution need time and must be done very carefully," he said. We cannot expect the cumulative reciprocal mistrust to be resolved with just one positive and constructive meeting. Iranian Deputy Foreign Minister Abbas Araqchi, who is taking a lead role in the negotiations, said Tuesday that the "negotiation's environment was positive," according to Iran's semiofficial Fararu news agency. U.S. Under Secretary of State Wendy Sherman and members of the U.S. delegation held a "useful" bilateral meeting with Araqchi and Iranian delegates Tuesday evening, the senior State Department official said. EU foreign policy chief Catherine Ashton is leading the talks for the P5+1 bloc. Opinion: Why there's room to strike a deal Thawing relations? This week's high-level talks in Geneva are the first such since the election of President Hassan Rouhani this summer raised the prospect of a shift in direction from Iran. Rouhani's visit culminated in a phone call with U.S. President Barack Obama and a meeting between U.S. Secretary of State John Kerry and Iran's Zarif. In another sign of easing tensions, Iran's state news agency IRNA reported Wednesday that Iran and Britain plan to introduce their nonresident charges d'affaires -- the level of diplomat below ambassador -- within two weeks. Tehran and London agreed to the step on October 8, after a telephone call between Zarif and his British counterpart, William Hague. The diplomats' mission will be to improve relations on the way to the eventual reopening of embassies, Hague said then. Asked about Wednesday's IRNA report, Britain's Foreign and Commonwealth Office told CNN that an announcement would be made in due course. Britain closed its embassy in Iran and evacuated its entire diplomatic staff from that country in late 2011 after hundreds of student protesters stormed the embassy and another British diplomatic compound. Hague also ordered the Iranian Embassy in London to close immediately, saying that Iran was in breach of its international obligations to protect diplomatic missions. As the latest talks in Geneva continue, Israel has warned against easing the punishing economic sanctions imposed against Iran too soon. Such a move would be a "historic mistake," Israeli Prime Minister Benjamin Netanyahu said Tuesday. "Now is an opportune moment to reach a genuine diplomatic solution that peacefully ends Iran's military nuclear program," he said. It is keen to resolve the issue "in a short period of time," he told CNN's Christiane Amanpour in an exclusive interview from Geneva. Opinion: How Tehran got back to the negotiating table CNN's Shirzad Bozorgmehr, Carol Jordan, Saad Abedine, Michael Schwartz and Elise Labott contributed to this report.