COPENHAGEN, Denmark -- UN Secretary-General Ban Ki-moon told nations that they had the chance to "change the course of our history" if they worked together to limit carbon emissions that are blamed for increasing global temperatures.

"We have a chance -- a real chance, here and now -- to change the course of our history," he said, noting that countries had to work quickly, because nature doesn't negotiate.

He urged both industrialized and developing countries to do more during this week's Copenhagen summit toward reaching an agreement on limiting the emissions, saying they "can and they must do more."

"This is a time to stop pointing fingers," Ban added. "This is a time to start looking in the mirror and offering what they can do more of."

US Secretary of State Hillary Clinton wrote Tuesday that the United States is ready to do their part to reduce greenhouse-gas emissions but that other countries, especially poorer ones, must play their parts as well.

Clinton's assertion came as a major international summit headed into the home stretch.

"Nearly all of the growth in emissions in the next 20 years will come from the developing world," Clinton wrote in an opinion piece for the International Herald Tribune. "Without their participation and commitment, a solution is impossible."

The divide between rich and poor countries is one of the key fissures at the UN conference on climate change in Denmark.

Developing countries object to restrictions that they fear would keep them from following the same path to prosperity taken by the United States and other industrialized nations.

The man running the conference warned Tuesday that "nowhere near enough progress" had been made toward an agreement.

"There is still an enormous amount of work and ground to be covered if this conference is to deliver what people around the world expect it to deliver," Yvo de Boer, executive secretary of the UN Framework Convention on Climate Change, said at a news conference.

Clinton's intervention into the debate comes the day before world leaders sit down in an attempt to hash out a final agreement. The "high-level segment" of the conference begins Wednesday.

President Obama is among leaders expected to attend the end of the summit. He's due to be in Copenhagen on Friday.

The United States announced an initiative Monday to support clean energy technologies in developing nations, funded by $350 million from industrialized countries.

US Energy Secretary Steven Chu committed $85 million of the total funding over five years and also announced an international meeting next year in Washington billed as the "first-ever Clean Energy Ministerial."

According to a news release from the Energy Department, the Renewables and Efficiency Deployment Initiative, or Climate REDI, "will accelerate deployment of renewable energy and energy efficiency technologies in developing countries -- reducing greenhouse gas emissions, fighting energy poverty and improving public health for the most vulnerable, particularly women and children."

The plan combines different programs to tackle a series of environmental challenges, including climate change. One focuses on getting solar home systems and LED lanterns to those without access to electricity, to help them avoid "expensive and polluting kerosene."

Another "will provide policy support and technical assistance to low-income countries developing national renewable energy strategies," according to the news release.

The plan is part of the Major Economies Forum on Energy and Climate, created by the Obama administration. It includes increasing the efforts of existing programs under the World Bank's Strategic Climate Fund.

Other nations contributing funds toward the global initiative include Italy, Australia, Britain, the Netherlands, Norway and Switzerland.