Russian President Vladimir Putin has called useful the Customs Union - Ukraine - European Commission meeting and said a Russia-Ukraine-EU working group would draw up proposals regarding Russian and Customs Union concerns about the Ukrainian intention to join the European Union before September 12.

"On the whole, my opinion is positive. The meeting held in that format was useful. We had an opportunity to formulate our concerns once again and we agreed to boost the activity of the trilateral working group comprising Russia, Ukraine and European Union representatives and to try to draw up proposals regarding the aforementioned concerns of Russia and the Customs Union before September 12," he told reporters in Minsk.