China and India will not attend the United Nations' summit on climate change. Their absence might undermine the meeting's purpose, which is to discuss reduction on global carbon emissions.

U.N. diplomats, who requested anonymity, confirmed that China President Xi Jinping and India Prime Minister Narendra Modi informed U.N. secretary general Ban Ki-moon that they couldn't join the meeting on Sept. 23.

"I was completely shocked and very disappointed to read today that Chinese President Xi and Indian Prime Minister Modi may not make it to Ban Ki-moon's Climate Summit," foreign minister of Marshall Islands, Tony deBrum, told Businessweek.

deBrum further explained that small island states, like Marshall Islands, are the most vulnerable to the effects of climate change. He said that developing countries should support global carbon emission cuts.

China is currently the No.1 emitter of greenhouse gas, while India sits in the third spot. According to data gathered by the World Bank, the combined carbon emissions of these two countries accounts for a third of global emissions. In addition, the countries' carbon footprint is increasing.

The Guardian reported that President Xi might be sending another senior Chinese politician to represent him in the summit.

Ban is still hoping that Modi will make it to the summit, as India can make significant contributions to the topic.

"I think the important issue for us is really on the commitments that countries will bring. And the Secretary-General expects every Member State to come with strong and bold commitments on climate change," Ban's spokesperson Stephane Dujarric told reporters, quoted by Economic Times.

After this one-day meeting, another session will be held in December in Peru, then London in 2015. The meeting will not focus on negotiation but will gather business executives, environmentalists and world leaders to come up with ways to mitigate global warming.