There is a persistent murmur in financial markets that the Trump administration may push through a grand bargain to weaken the overvalued U.S. dollar. But there are multiple problems here, not least Europe's likely unwillingness to play ball.

U.S. stock futures and the dollar were both sliding on Friday as Asian markets rallied after President Trump signaled he wouldn’t rush to raise tariffs on China. The moves came after Trump said he “would rather not” hike levies on imports from China,