Leonid Bershidsky: U.S. wants European cooperation on defense. Or else.

The U.S. appears to be stepping up the defense demands it makes of European allies - a development that could complicate trade talks between the U.S. and the European Union.Spiegel Online reported Tuesday that two Trump administration officials have written a letter to top EU diplomat Federica Mogherini to express their displeasure with the European effort to streamline procurement and with the fund the EU has created to develop new weapons. The letter, signed by Ellen Lord, the Pentagon's lead