The Obama administration said Wednesday it has raised concerns with Tanzania's government about the impact of its plan to build a road through the Serengeti wildlife reserve, which environmentalists say could affect the famed wildebeest migration and threaten endangered species. The top U.S. diplomat for Africa, Johnnie Carson, said he brought the matter up in meetings with top Tanzanian officials in late April and that Secretary of State Hillary Rodham Clinton could revisit the topic when she visits the country this month. Clinton is expected in Tanzania next week as part of a three-nation African tour focused on trade and...