BRATISLAVA - Slovak Prime Minister Robert Fico on Monday voiced opposition to Ukraine's use of US long-range missiles to strike inside Russia, the News Agency of the Slovak Republic (TASR) reported.

In a major shift of his administration's policy on the Ukraine crisis, US President Joe Biden has authorized Kiev to use US-supplied long-range missiles to strike targets inside Russia, US media reported Sunday.

The greenlight would allow the Ukrainian troop's first use of Western-made ATACMS missiles, reported US media outlets including The Associated Press, The New York Times and The Washington Post, citing two anonymous US officials.

Fico has instructed the country's Foreign Minister Juraj Blanar and Defence Minister Robert Kalinak not to support the move, TASR reported.

"This is an unprecedented escalation of tensions," the Government Office cited Fico as saying, according to the report.