By Humeyra Pamuk, Michael Martina and David Brunnstrom WASHINGTON (Reuters) -The United States does not seek to sever China from the global economy, but wants Beijing to adhere to international rules, U.S. Secretary of State Antony Blinken said in a long-awaited speech on Thursday on U.S. strategy to address China’s rise as a great power. Washington will not block China from growing its economy or try to change Beijing’s political system, Blinken said, but it will defend international law and institutions that maintain peace and security and make it possible for countries, including the United…