The United States is making a hard push for a much larger South Korean share in the cost of stationing American troops here than what Seoul is willing to pay, local government sources said on Sunday, casting doubt over the two sides' impending negotiations over the issue. The two countries will open a new round of talks on Thursday in Seoul to renew the Special Measure Agreement (SMA), under which they will decide how to split the cost of stationing 28,500 U.S. troops in South Korea.