The Obama administration said on Tuesday it had achieved a breakthrough in negotiations with China to eliminate tariffs on an array of information technology products, from video-game consoles and computer software to medical equipment and semiconductors. The understanding, reached during a visit to China by President Barack Obama, opens the door to expanding a World Trade Organization treaty on these products, assuming other countries can be persuaded to accept the same terms. American officials predicted a broader deal would be reached swiftly now that it had resolved longstanding ...