HONG KONG — Even as China has set ambitious goals for itself in clean-energy production and reduction of global warming gases, the country’s surging demand for power from oil and coal has led to the largest six-month increase in the tonnage of human generated greenhouse gases ever by a single country.

China’s leaders are so concerned about rising energy use and declining energy efficiency that the cabinet held a special meeting this week to discuss the problem, according to a statement Thursday from the ministry of industry and information technology. Coal-fired electricity and oil sales each climbed 24 percent in the first quarter from a year earlier, on the heels of similar increases in the fourth quarter

Premier Wen Jiabao promised tougher policies to enforce energy conservation, including a ban on government approval of any new projects by companies that failed to eliminate inefficient capacity, the ministry said. Mr. Wen also said that China had to find a way to meet the target in its current five-year plan of a 20 percent improvement in energy efficiency.

“We can never break our pledge, stagger our resolution or weaken our efforts, no matter how difficult it is,” Mr. Wen said. Western experts say it will be hard to meet the target, but that China’s leaders seem determined.

“No country of this size has seen energy demand grow this fast before in absolute terms, and those who are most concerned about this are the Chinese themselves,” said Jonathan Sinton, the China program manager at the International Energy Agency in Paris.

China has been the world’s largest emitter of greenhouse gases each year since 2006, leading the United States by an ever-widening margin. A failure by China to meet its own energy efficiency targets would be a big setback for international efforts to limit such emissions.

Such a failure would also be a potential diplomatic embarrassment for the Chinese government, which promised the world just before the Copenhagen climate summit meeting in December that it would improve energy efficiency.

The issue has major economic implications for China and for global energy markets. The nation’s ravenous appetite for fossil fuels is driven by China’s shifting economic base — away from light export industries like garment and shoe production and toward energy-intensive heavy industries like steel and cement manufacturing for cars and construction for the domestic market.

Almost all urban households in China now have a washing machine, a refrigerator and an air-conditioner, according to government statistics. Rural ownership of appliances is now soaring as well because of new government subsidies for their purchase since late 2008.

Car ownership is rising rapidly in the cities, while bicycle ownership is actually falling in rural areas as more families buy motorcycles and light trucks.

General Motors announced on Thursday that its sales in China rose 41 percent in April from a year earlier, virtually all of the vehicles made in China because of high import taxes.

Zhou Xi’an, a National Energy Administration official, said in a statement last month that fossil fuel consumption was likely to increase further in the second quarter of this year because of rising car ownership, diesel use in the increasingly mechanized agricultural sector and extra jet fuel consumption for travelers to the Shanghai Expo.

The shift in the composition of China’s economic output is overwhelming the effects of China’s rapid expansion of renewable energy and its existing energy conservation program, energy experts said.

The increase in oil and coal-fired electricity consumption in the first quarter was twice as fast as economic growth of about 12 percent for that period, a sign that rising energy consumption is not just the result of a rebounding economy but also of changes in the mix of industrial activity. The shift in activity is partly because of China’s economic stimulus program, which has resulted in a surge in public works construction that requires a lot of steel and cement.

Burning fossil fuels releases carbon dioxide, which many scientists describe as the biggest man-made contributor to global warming.

President Hu Jintao pledged in November that by 2020 the Chinese government would slow its growth in greenhouse gases by sharply improving energy efficiency. Mr. Wen went to the Copenhagen climate meeting three weeks later and opposed any international monitoring of China’s energy efficiency effort or binding limits on China’s overall energy consumption.

China’s current five-year plan, from 2006 to 2010, already sets an efficiency target that the country may now be less likely to meet.