Israel and the US canceled a missile defense drill, billed as the largest ever in the country's history, planned for the spring, senior military officials said Sunday.Initially scheduled for April and called "Austere Challenge," the drill was supposed to see the deployment of thousands of US troops and various sophisticated US military equipment in Israel.RELATED:US looking for assurances J'lem won't strike IranNetanyahu, Obama talk Mideast peace, IranIn recent weeks, Defense Minister Ehud Barak's office has held talks with the Pentagon about the possibility of canceling the drill.Senior military officers told The Jerusalem Post that the drill scheduled for April has been canceled, while defense officials said that it was possible that it would be held later in 2012. The drill, expected to involve the deployment of thousands of US troops in Israel, was scheduled to last around a week and mark the first time that a top US military commander would participate in the simulations.The parties were scheduled to simulate missile defense scenarios with the objective of creating a high level of interoperability so that, if needed, US missile defense systems would be able to work with Israeli systems during a conflict. Officials refused to elaborate on the reasons behind talks to postpone or cancel the drill, but said they were mostly "technical and logistical."Talks about postponing the drill took the Americans, as well as the Israeli Air Defense division, responsible for missile defense, by surprise. Just last Thursday, top IAF officers had said that the drill was scheduled for this spring. This year’s drill was expected to be unique in its size and scope and also mark the first time that commander of the US European Command, Adm. James Stavridis, would participate in the simulations. In the event of war, the EUCOM commander will be responsible for approving Israeli requests to deploy US missile defense systems in Israel.The planned drill had caused tension in the region amid concern that Israel is planning an attack against Iran's nuclear facilities in the near future, and therefore is bolstering its defenses together with the US.It is possible that talks about postponing the drill can also be contributed to increased American concern that an Israeli strike is being planned. Later this week, IDF Chief of Staff Lt.-Gen. Benny Gantz will fly to Brussels for a meeting of NATO military commanders and will return to Israel on Thursday to greet Gen. Martin Dempsey, chairman of the US Joint Chiefs of Staff, who will be arriving in Tel Aviv for his first official visit.