President Vladimir Putin said Thursday that Russia is "still open" to talks on Ukraine's gas debt, accusing the EU of failing to make specific proposals to help prevent a cutoff of supplies from next month. In an open letter to European leaders, Putin also called on Brussels to "more actively engage" in finding ways to stabilise crisis-hit Ukraine'economy. "Unfortunately, we have to say that we have not received any specific proposals from our partners as to how to stabilise the situation," Putin said in the letter released by the Kremlin. He said Russia was "forced" to threaten to cut off gas supplies from June 3 after switching to up-front payments because Ukraine has amassed a gas debt of $3.5 billion (2.6 billion euros). "The Russian Federation is still open to continue consultations and work together with European countries in order to normalise the situation," Putin said. "We also hope that the European Commission will more actively engage in dialogue in order to work out specific and fair solutions that will help stabilise the Ukrainian economy." Nearly 15 percent of all gas consumed in Europe is delivered from Russia via Ukraine and Brussels fears that a cutoff could lead to disruptions in supplies to the EU.