Russia's foreign minister insisted on Sunday that a flagship project to pipe natural gas to Europe would be finished, despite the United States slapping sanctions on the companies involved.

Sergei Lavrov said the US measures over Nord Stream 2 had "humiliated" European countries but reiterated Moscow's commitment to the plan, in comments to be broadcast on Sunday on Pervy Kanal, a state TV channel.

The American announcement of asset freezes and visa bans enraged Germany and the European Union and immediately led to a Swiss pipe-laying contractor suspending its work on the project.

But the US envoy to Germany insisted it was a "very pro-European decision" to block the pipeline, due to double supplies of Russian gas flowing to Western Europe via an undersea pipe to Germany from early 2020.

"I've been hearing all day from European diplomats thanking me for taking this action," Richard Grenell told German newspaper Bild.

American lawmakers argued that Nord Stream 2 would give Russia too much influence over security and economic issues in western Europe.

The pipeline would also allow Russia to reroute supplies from overland pipes running through Ukraine, with Kiev long expressing concerns that this would deprive them of vital leverage over its giant neighbour.

The sanctions were welcomed by Ukraine and Poland, which labelled the pipeline "an instrument for the realisation of Russian economic and, potentially, military policy".

However, Lavrov said Nord Stream 2 would help with both the economy and the long-term energy security of European countries.

"They have been humiliated. But we have heard words, especially from Berlin, that show that the self-esteem of our European partners is still intact," he said.

Germany reacted angrily to the sanctions on Saturday, accusing the US of interfering in its internal affairs.

More than 80% of the pipeline under the Baltic has been completed for the project, which is half-financed by Russia's state-owned Gazprom and half by five European companies.