The White House pledged Friday to clamp down on US emissions of methane, a greenhouse gas produced by cattle and natural gas production that contributes to climate change. The bid is the latest by President Barack Obama's administration to find ways to tackle climate change in the face of staunch opposition by rival Republican lawmakers. The United States is the largest greenhouse gas emitter after China. Methane makes up some nine percent of US emissions but the environmental effect is some 20 times as potent as that of the most common greenhouse gas, carbon dioxide. Cow manure is a leading source of methane. The White House said that the dairy industry and federal departments would unveil in June voluntary plans to reduce the sector's emissions by 25 percent by 2020. Separately, the Environmental Protection Agency will meet experts on methane emissions from oil and gas to see if there is a need for more regulations, which would be unveiled by the end of 2016, the White House said. Within the current year, the agency will propose new standards on landfills and a separate federal body, the Bureau of Land Management, will update regulations to reduce venting and flaring from oil and gas production on public lands, it said. The White House did not set an overall goal on reducing methane but said it was committed to Obama's target of cutting overall greenhouse gas emissions by 17 percent by 2020 from 2005 levels. Many environmentalists say that the commitment by the United States and other countries is nowhere close to the reduction levels needed to avert worst-case scenarios of climate change. Scientists with the UN's Intergovernmental Panel on Climate Change have been meeting this week in Yokohama, Japan to hammer out the latest part of a massive report on the issue. A draft, seen by AFP, says that global warming has resulted in reduced yields of wheat, rice and corn, and spells out the possibility of increased floods, drought and conflict if emissions are unchecked. Obama has pledged action on climate change but increasingly focused on actions he can take without Congress. A proposal for broader restrictions on greenhouse emissions died in the Senate in 2010 amid opposition by lawmakers close to industry.