President Trump swiped at the Federal Reserve while criticizing China and the European Union in tweets on Friday, complaining that currency manipulation is "taking away our big competitive edge. ... As usual, not a level playing field."

Why it matters: The trade war between the U.S. and other countries is shifting into a currency war. This is the second time this week Trump has roiled currency markets with comments about Fed policy. The dollar fell shortly after Trump's tweets.

• Our thought bubble... Axios' Dan Primack says: "Trump pledged during the campaign to label China a currency manipulator but, once in office, chose against actually doing so. Probably because his own Treasury Department said it wasn't true."

Go deeper: The WSJ's Greg Ip on what Trump is missing with his Fed criticism.

• "Mr. Trump is especially upset by the dollar’s rise, which threatens to widen the trade deficit which he badly wants to shrink. Yet the Fed is the secondary player here. The dollar is up against the euro because Mr. Trump’s tax cut is lifting U.S. growth above Europe’s."
• "The bigger problem—for the president and the Fed—is optics. ... His schedules show that since becoming chairman, he has not met with Mr. Trump; given the arched eyebrows it’s sure to provoke, he’ll think twice before doing so now. And that’s a pity because there may be times, for example during a crisis, when for the good of the country he should."