US President Barack Obama urged all NATO member countries to play a role in helping stabilise Afghanistan.Emerging from a meeting with NATO Secretary General Jens Stoltenberg at the White House, Obama on Tuesday said not only the US, but also all NATO members should offer training and other support to Afghan forces following the drawdown of NATO troops, Xinhua reported.Obama said the issue would be discussed at a NATO summit slated for July 2016 in the Polish capital city of Warsaw.American and NATO troops ended their combat role in Afghanistan at the end of 2014, with some 12,000 coalition troops remaining in the Asian country to play supporting roles.In March, Obama agreed to maintain the current level of 9,800 US troops until the end of 2015, in a departure from his original plan to reduce it to some 5,500, following a meeting with Afghan President Ashraf Ghani at the White House.On the situation in Ukraine, Obama accused Russia of taking an "increasingly aggressive posture" in the country's east, while Stoltenberg called for a "full implementation" of cease-fire agreements and urged Russia to withdraw its forces from Ukraine.The NATO chief said he and Obama have a "common understanding" that the military bloc is facing a "new security environment."