Ukrainian President Petro Poroshenko speaks to the press in front of Ukraine’s state coat of arms on Sept. 12. Agence France-Presse/Getty Images KIEV, Ukraine—Ukrainian President Petro Poroshenko faces rising criticism for his decision to delay implementation of part of a European Union deal to avoid threatened Russian retaliation. A senior diplomat resigned in protest over the weekend, and pro-European politicians who are competing with Mr. Poroshenko’s party in parliamentary elections next month blasted the decision as caving to Russia, which wants Ukraine to give up the deal and remain in its orbit. The tensions highlight how difficult it will be for Mr. Poroshenko to manage the competing pressures of a Kremlin that isn’t backing down and a domestic electorate that wants closer ties to Europe and no concessions to Moscow. On Friday, Ukraine and the EU agreed to put off implementing a landmark trade deal , which is part […]