The Commission is seeking a new date for a meeting, the government of Slovakia's pro-Russian Prime Minister Robert Fico said in a statement.
Fico has accused Kyiv of damaging Slovakia by not extending a transit deal for Russian gas, and has threatened to cut electricity flows to Ukraine and reduce aid for its refugees.
Kyiv has said the end of gas transit deprives Moscow of revenue as long as Russia continues to attack Ukraine.
Slovakia has arranged alternative gas sources and routes, but Fico has argued that the end of Ukraine's transit of Russian gas meant that Slovakia lost its own transit revenue and had to pay more to bring gas from elsewhere.
Fico put the cost for Slovakia at 500 million euros ($519 million) and said he would seek the restart of the flows or compensation. The Slovak government caps gas prices, so may face increased costs if it pays more for gas.
Ukrainian President Volodymyr Zelenskiy has accused Fico of opening a "second energy front" against Ukraine on the orders of Russia.
Ukraine, whose power infrastructure has suffered from Russian bombing, has synchronised its grid with the European Union and has been trading electricity through high-voltage connections with Poland, Slovakia, Hungary and Romania.
Its energy minister has said Ukraine could make up for a potential cut in flows from Slovakia, which accounted for about 20% of the country's imports.
It was not immediately clear how Fico planned to restrict the flows, which include commercial supplies as well as emergency aid, at times when Ukraine needs it.
