LONDON — The United States and Ukraine signed a new partnership document on Thursday that will enhance Ukraine’s defenses and allow for more cooperation between the two countries on reforming Ukraine’s military structure. Secretary of Defense Ash Carter and Ukrainian Minister of Defense Stepan Poltorak signed the Partner Concept during a bilateral meeting on the sidelines of the UN Peacekeeping Ministerial in London. This Partner Concept will build on the strong partnership between the U.S. and Ukraine and will enhance the effectiveness of U.S. security assistance efforts, according to a readout of the meeting. Carter spoke with reporters about the new agreement briefly at the airport in England before flying to Norway. He said it will cover assistance on everything from training to acquisition. It’s about Ukrainian capability for defending its own territory, that’s been the objective of all of our assistance to Ukraine so it continues in the same vein, Carter said. It just allows us greatly to strengthen that and get it off an ad hoc basis of the last two years reacting to events and put it on, in this case a five-year horizon.