High-level talks aimed at forging a global climate change deal were officially declared open at a ceremony in Copenhagen on Tuesday, according to dpa. The ceremony was attended by Danish Prime Minister Lars Lokke Rasmussen, UN Secretary General Ban Ki-moon, the Prince of Wales and other dignitaries. The high-level talks are to be conducted by environment ministers over the next two days, with world leaders expected to seal a deal by the end of the week. So far, the negotiations have been conducted by bureaucrats from nearly 200 national delegations. The 12-day United Nations Climate Change Conference opened on December 7 and is due to end on Friday.