With two weeks of international negotiations over how to implement the Kyoto climate change treaty beginning today in The Hague, Netherlands, President Clinton on Saturday called for the first time for federal regulations that would limit emissions of the greenhouse gas carbon dioxide from power plants in the U.S. Clinton proposed a trading system, similar to the one now in place for the pollutants that cause acid rain, under which the government would set a national cap on CO2 emissions from power plants and divide pollution permits among the plants. Power companies could reduce their emissions beyond required levels and sell leftover pollution credits to companies that weren’t able to cut emissions adequately. Because the U.S. accounted for 36 percent of the world’s greenhouse gas emissions in 1990, European negotiators in The Hague would like the U.S. to achieve most of its greenhouse gas emissions cuts domestically. But Clinton administration negotiators will push for an international pollution-trading system so that U.S. companies can pay for emissions reductions abroad. In another clash with Europe, the U.S. wants to count carbon sinks like forests that may absorb CO2 from the atmosphere toward its required emissions cuts, rather than cutting emissions at the source.