Germany's Foreign Minister Sigmar Gabriel, left, and Austria's Federal Chancellor Christian Kern | Herbert Neubauer/AFP via Getty Images Germany and Austria warn US over expanded Russia sanctions ‘Europe’s energy supply is a matter for Europe, and not for the United States of America.’

Germany and Austria on Thursday hit back at proposed U.S. sanctions that would threaten European companies participating in the Nord Stream 2 pipeline project, accusing the U.S. of politicizing its economic interest in selling natural gas to Europe.

"Europe's energy supply is a matter for Europe, and not for the United States of America," Germany's Foreign Minister Sigmar Gabriel and Austria's Federal Chancellor Christian Kern said in a joint statement.

U.S. senators on Wednesday supported extending and expanding sanctions against Moscow.

The two politicians warned that it wouldn't "only be highly regrettable, but also damaging" to their countries' cooperation on the Ukraine crisis if "irrelevant considerations such as U.S. economic interest in exporting gas were to gain the upper hand." At the heart of their push-back is the planned expansion of the Nord Stream gas pipeline between Russia and Germany.

"To threaten companies from Germany, Austria and other European states with penalties on the U.S. market if they participate in natural gas projects such as Nord Stream 2 with Russia or finance them introduces a completely new and very negative quality into European-American relations," they said.

The Russian pipeline project has split Europe, too. The European Commission and Eastern European and Baltic countries have long opposed it over concerns that it would tighten Moscow’s grip on the region’s gas market and undermine EU efforts to diversify supplies. Western European countries, especially Germany, instead argue it's a commercial project.

The pipeline's project company Nord Stream 2 said the threats signaled "increasing politicization ... driven by commercial interests."