Reuters: The United States will pledge to cut its greenhouse gas emissions by 17 percent by 2020 at a U.N. climate change meeting in December, the White House said on Wednesday. Obama’s negotiating position for the talks in Copenhagen has been hampered by slow progress on a climate bill in the U.S. Senate. The U.S. House of Representatives passed a bill that sets a 17 percent reduction target for emissions by 2020 from 2005 levels. A Senate version aims for a 20 percent cut. The …