On March 18, US Secretary of State Antony Blinken issued a warning to entities involved in the Nord Stream 2 project that they risk "US sanctions and should immediately abandon work on the pipeline."

"We will continue to register any organization that may be involved in any sanctioned activity, and have made it clear that any company risks being penalized for participating in Nord Stream 2," Giordono-Scholz said.

Iran has insisted that the US drop all the sanctions it unilaterally imposed after withdrawing from the deal in 2018, while US officials have maintained that Iranian nuclear violations of the agreement must be rectified first.

Iran met in Vienna with the remaining signatories of the deal – the EU, UK, France, Russia, China and Germany. While the US was also in Vienna, it did not participate directly in those talks but met separately with the deal signatories in a different part of the city.

Iranian crude production has risen in recent months, hitting 2.14 million b/d in February, a 190,000 b/d increase from a 33-year low of 1.95 million b/d in August.

The number of cases of low-flying "foreign planes" over the Nord Stream 2's vessels has increased in the second half of March.

However, Russian gas remains competitive for European buyers given its low-cost production base and long-term reliability.

Between 2015 and 2020, U.S. gas production grew roughly twice as fast (4.3% per year on average) as consumption (2.3% per year), according to data from the U.S. Energy Information Administration.

"Based on this document, China will be a steady importer of Iran's oil, and Iran should remove China's concerns for return of its investment,"

“It has the potential to undermine the interests of Ukraine, Poland and a number of close partners and allies,” Blinken added, saying that a U.S. law required Washington to impose sanctions on companies participating in the Nord Stream 2 project.

The consortium behind Nord Stream 2 has pushed ahead with construction despite growing political pressure.

Being able to use two pipelaying vessels will speed up work on completing Nord Stream 2, which before the Fortuna resumed work had around 150 km left to lay out of a total 2,460 km of the two-string pipeline.

"The US has decided to put the Nord Stream 2 project in a broader geopolitical framework and is threatening all industries or parties involved in the project with sanctions," Wintershall Dea said.

There had been calls for the Biden administration to intensify sanctions designations to include a wide range of companies involved in the construction of Nord Stream 2, including service companies, insurers and certification companies.

Despite U.S. sanctions against the pipeline, Berlin has stood by Nord Stream 2, which it says is a commercial project.