The United States has agreed to notify other nations before it launches most ballistic missile tests or satellites, in a measure that builds on a landmark arms agreement with Russia and is meant to encourage Moscow to reciprocate. The American decision was contained in a confidential note made available Thursday to The Associated Press and confirmed by three diplomats familiar with the issue. The move is less far-reaching — or binding — than the treaty signed last month by the U.S. and Russian presidents that outlines cuts in both nations' massive nuclear arsenals. But it is significant in reflecting Washington's...