Sign up now for FREE unlimited access to Reuters.comSign up WASHINGTON, Sept 11 (Reuters) – U.S. Treasury Secretary Janet Yellen said on Sunday that Americans may experience a spike in natural gas prices this winter when the European Union significantly cuts its purchase of Russian oil, adding that a proposed price ceiling on Russia’s oil exports is designed to keep prices under control. “It’s a risk, and it’s a risk that we’re working on the price ceiling to try to address,” Yellen told CNN. The possible price increase could come because the EU will “mostly stop buying Russian oil” and impose a ban on services that allow Russia to transport oil by tanker, he said. The price cap plan agreed by the G7 rich nations calls on participating countries to deny insurance, financing, brokerage, shipping and other services to oil cargoes priced above a yet-to-be-agreed crude and oil product price cap. be determined. Yellen said the price cap was aimed at reducing revenue that Russia could use to wage war in Ukraine while maintaining Russian oil supplies to keep global prices low. Sign up now for FREE unlimited access to Reuters.comSign up Reporting by Katharine Jackson Editing by Bill Berkrot Our Standards: The Thomson Reuters Trust Principles.