"I consider sanctions meaningless and counterproductive," Mr Fico told reporters early on Sunday after meeting fellow EU leaders in Brussels.
"Until we know the impact of the already imposed sanctions, it makes no sense to impose new ones."
EU leaders asked the European Commission, the EU executive, to draw up proposals for new sanctions on Russia over its action in Ukraine within a week, though they did not say when they could be implemented.
"Should there be proposals," he said, "I reserve a right to veto sanctions harming national interests of Slovakia."
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