Representatives from more than 160 countries began formal negotiations here Monday on a treaty to mitigate climate change, with the secretary general of the United Nations, Ban Ki Moon, urging governments to help in "saving the planet." The talks, which are scheduled to conclude at the end of 2009, come three months after a rancorous meeting in Indonesia that exposed deep fissures in how countries plan to battle global warming. "Saving our planet requires you to be ambitious in what you aim and, equally, in how hard you work to reach your goal," Ban told delegates in a prerecorded video message. No breakthroughs are expected at the weeklong meeting in Bangkok, which is mainly intended to lay out the agenda for a series of subsequent sessions. "We see this as very much a process-oriented meeting, no negotiations per se on numbers," said Harlan Watson, the negotiator representing the United States at the talks. One of the main challenges for negotiators over the next 21 months will be reintroducing the United States into a global system of emissions reductions. The United States signed but never ratified the Kyoto Protocol, the 1997 agreement that binds wealthy countries to specific cuts in greenhouse gases. The new treaty would replace the Kyoto Protocol, although some provisions of the previous treaty would remain. Angela Anderson, director of the global warming program at the Pew Charitable Trusts, an American nonpartisan organization, said that negotiators were watching the U.S. election campaign closely for signs of future changes in U.S. climate change policy. "We have three presidential candidates, all of whom have said they will re-engage in climate negotiations," she said. "There will definitely be a new voice in the U.S." The November presidential election will come roughly halfway through the negotiations, and many here believe negotiators will defer tough decisions until a new president is inaugurated. The American public also appears more aware of the issue of global warming now than at the start of the Bush administration. Al Gore, the former U.S. vice president and a Nobel Prize winner for his environmental advocacy, is due to begin a $300 million advertising campaign to encourage Americans to push for aggressive reductions in greenhouse emissions, according to media reports. But the United States is by no means the only potential obstacle to a global climate treaty. Countries disagree over what role wealthy and poor countries should play in reducing emissions. And even among wealthy countries there is significant discord. Last week, the Japanese vice trade minister, Takao Kitabata, said the method used to measure cuts in greenhouse gases in the Kyoto Protocol was "extremely unfair." Countries also disagree on how much to compensate developing countries for their efforts in reducing global warming. The agreement reached on the Indonesian resort island of Bali in December called for wealthier countries to help finance cleaner technologies and non-fossil-fuel alternatives in developing countries.