KYIV - Ukraine's state gas company and gas infrastructure operator have issued a demand to the German government to either halt or severely curtail gas flows through the Nord Stream 1 pipeline, the head of the gas system operator said on Friday.

"With Naftogaz we sent an appeal to the German economy ministry and the German regulator... on the suspension of Nord Stream 1," the head of Ukraine's gas system operator Serhiy Makogon told national television.

Ukraine is willing and able to provide an alternate transport route to the pipeline, which runs under the Baltic, he said.

Germany has already halted Russia's Nord Stream 2 gas project, which was designed to double gas shipments into Germany, as punishment for Russia's February invasion of Ukraine. The $11 billion project finished construction late last year but has never started.

Diverting shipments from the existing Nord Stream 1 pipeline might be a tough sell for Germany and the rest of Europe, analysts say.

The demand argues that the operation of the pipeline is allowed under German law on the basis that it contributes to the strengthening of the security of gas supplies to Europe, but that Russia had violated those principles.

"We see that Russia violates these principles: creating an artificial gas deficit last year; unilaterally insisting on payment in roubles; suspending gas supplies to Poland, Finland and Bulgaria" as well as invading Ukraine, Makogon said.

(Reporting by Natalia Zinets; Writing by Conor Humphries; Editing by Louise Heavens)