KYIV, Oct 1 - Ukraine called on the United States and Germany on Friday to impose sanctions on Russia's Gazprom, which it accused of using energy as a weapon after the energy giant implemented a transit deal with Hungary that deprives Kyiv of gas supplies, Reuters reported.

Under the terms of a long-term supply deal with Budapest that kicked in on Friday, Gazprom will no longer ship its gas to Hungary via Ukraine, but will send it via Serbia and Austria instead.

That deprives Ukraine of transit revenues and also means it can no longer import reverse flow gas via Hungary, which it has been doing since 2015 as a way of not buying gas directly from Russia.

Ties with Moscow have been in crisis since its annexation of Crimea in 2014 and backing for a separatist uprising in eastern Ukraine.

Yuriy Vitrenko, the head of Ukraine's Naftogaz, called on Washington and Germany to honor what he said were pledges to get tough with Moscow made in the context of the separate Nord Stream 2 gas pipeline to Germany.

"The Kremlin is doing this on purpose. It's not even sabre rattling, it's the obvious use of gas as a weapon," Vitrenko said on Facebook.

"A joint statement from the United States and Germany said that if the Kremlin used gas as a weapon, there would be an appropriate response. We are now waiting for the imposition of sanctions on a 100% subsidiary of Gazprom, the operator of Nord Stream 2."

He was referring to an agreement between Berlin and Washington on Nord Stream 2 struck in July.

The dispute comes at a sensitive time for Russia, which wants Germany to certify the Nord Stream 2 gas pipeline to Germany now that it has been completed. Russia faces accusations from Kremlin critics that it is trying to speed up that approval process by deliberately not doing enough to supply Europe with gas during an energy crunch that has seen spot gas prices soar.

Russia denies the allegations.

There was no immediate response from Washington or Berlin to Vitrenko's call. The Kremlin dismissed Ukrainian criticism as unfounded and politicized.

Kremlin spokesman Dmitry Peskov said Russia was fulfilling all its obligations under existing natural gas contracts. (om/ez)