As G7 leaders converge on Kananaskis in the Canadian Rockies this weekend, the prospect of decisively tougher sanctions on Russia will loom large.

"Slovakia will not support the upcoming 18th sanctions package against Russia unless the European Commission provides it with a real solution to the crisis situation that Slovakia will find itself in after the complete cessation of gas, oil and nuclear fuel supplies from Russia," Fico wrote in a Facebook post late on Tuesday.

The European Commission proposed on Tuesday an 18th package of sanctions against Russia for its invasion of Ukraine, aimed at Moscow's energy revenues, its banks and its military industry.