Dan Mullaney, former Assistant U.S. Trade Representative for Europe and the Middle East, said he believes Trump's message to the European Union was aimed at pushing the EU to reach a better deal. Trump had previously threatened to impose a 50% tariff on the EU back in May, a move that seemed to expedite the negotiation process.

However, Mullaney said that this letter may encourage those within the EU who are inclined towards retaliation, as they believe the U.S. is not serious about reaching an agreement. He said, "These people will feel that their views are justified." (FXStreet)