(Reuters) - The loss of Malaysian Airlines flight MH17 must prove a catalyst for changing Russia's approach and ending the conflict in Ukraine, Prime Minister David Cameron wrote on Friday in an opinion piece in the New York Daily News. Russia has been attempting to destabilise a sovereign state, violate its territorial integrity and arm and train thuggish militias, he wrote, and the world has paid the price. Cameron has been pushing the European Union to impose harder-hitting sanctions on Russia after the downing of a Malaysian airliner in Ukraine, advocating an EU ban on future sales of military equipment to Moscow.

US President Barack Obama joined with the leaders of Australia and the Netherlands to demand full access to the crash site of flight MH17. Speaking in telephone calls with Australia Prime Minister Tony Abbott and Dutch counterpart Mark Rutte, the leaders agreed to work for a full investigation into the shooting down of the Malaysia Airlines jet last week. Obama and Abbott agreed that a "prompt, full, unimpeded and transparent international investigation is an imperative," a White House statement said. "The two leaders reaffirmed their commitment to assure that the crash site is properly secured, that all remains are found and returned home, and that a full, transparent and unhindered international investigation can proceed," the White House said.