Ukraine's move will deprive Russia of about $6.5 billion in annual revenue from gas sales to Europe, according to U.S. National Security Council spokesperson John Kirby.

With transit routes through Ukraine for Russian gas cut off, a few EU countries now need to rethink their gas supply. For others – including Germany and Switzerland – the impact will be minimal.

Slovak Prime Minister Robert Fico has expanded his threats against Ukraine over Kyiv's suspension of Russian natural gas transit. Source: Teraz.sk, citing Fico's words in Brussels after talks with European Commission officials on 9 January,

The historic first marks a milestone in Washington’s bid to replace Russia as Europe’s top source of natural gas.

Russian gas supplies sent via Ukraine to Europe for more than 40 years are scheduled to end on January 1 after Ukraine's Naftogaz refused to renew its latest five-year transit deal with Russia's Gazprom.

Russia will no longer transport gas to Europe via Ukraine’s pipelines, further limiting its ability to raise capital

The ongoing conflict has highlighted the importance of diversifying gas supplies to build resilience against geopolitical risks.

Ukrainian transit gas deal to Europe ended on Jan. 1. For now, the most acute effects are being felt in a region called Transnistria, on the eastern edge of Moldova.

Ukraine loses billions in gas transit fees, Europe faces soaring energy prices, with Russia largely insulated from the fallout