Ukrainian President Petro Poroshenko has insisted that the Minsk agreements on regulating the conflict in eastern Ukraine be fully implemented by the end of this year.
"The implementation…should end in 2015 and cannot be extended," he said at a conference Kyiv on September 11.
He said he had instructed his representative at the Minsk talks, former President Leonid Kuchma, to reject any efforts to extend the process into 2016.
Such an idea was previously raised by European Parliament President Martin Schulz and was endorsed by representatives of the Russia-backed separatists in the Luhansk and Donetsk regions.
He called for "enhanced restrictive measures" by the international community if Moscow continues to occupy Crimea and "hinder the settlement process" in the east.
Poroshenko also said that Moscow had stepped up its activity in Syria because it did not get "an immediate, powerful response" when it annexed the Ukrainian region of Crimea in March 2014.
"Today the so-called little green men are landing in Syria, instigating the an increase in violence in the Middle East, and provoking a further increase in the number of refugees going to the EU," Poroshenko said.