WASHINGTON — President Trump on Wednesday tried to increase pressure on China to change its trade practices by directing administration officials to consider more than doubling the size of proposed tariffs he has already threatened to slap on $200 billion in imports. But the administration stopped short of actually making such a move, raising questions about whether it was a negotiating ploy in its widening trade war with China. A week after moving to ease trade tensions with the European Union, the administration said it would consider imposing a 25 percent tariff on certain Chinese imports, up from the 10 percent Trump proposed last month. Senior administration officials expressed frustration Wednesday that China has responded to U.S.