The State Department said it has issued a "Fact Sheet on US Opposition to Nord Stream 2" and noted that it has up to 60 days to issue a report to Congress identifying "violating entities."
The State Department also said it has promised to act "expeditiously" on the matter.
Earlier in the day, Russia's Energy Minister Alexander Novak said that Nord Stream 2 will be launched before the end of 2020 despite US sanctions against the project.
Last week, US President Donald Trump signed a 2020 defence bill which, among other things, included sanctions against the Nord Stream 2 pipeline. Swiss company Allseas that had been laying pipes for the project has suspended its work already.