The department's review, required by Congress, concludes that Nord Stream 2 AG and CEO Matthias Warnig, an ally of Russian President Vladimir Putin, engaged in sanctionable activity but that it was in the US national interests to waive the sanctions, the source said.
Russian officials on Wednesday signaled that the move could help mend Washington's fraught ties with Moscow.
"This project is of great importance for the security of supply of the European gas market, it is therefore Europe's responsibility to decide," Seele told Austrian newspaper Wiener Zeitung.
"We have had a deep transatlantic friendship with the USA for decades. And friends shouldn't threaten each other," he said in an interview published on Saturday.
The vessel departed from the German port of Wismar on Thursday, Refinitiv Eikon ship-tracking data showed, as the Nord Stream 2 consortium pushes to complete construction of the gas pipeline.
The US has been threatening sanctions against European companies that support construction of the $11 billion gas pipeline, and Zurich Insurance Group dropped out last month.
Munich Re Syndicate has issued the notice of termination to Nord Stream 2," a spokesman said in an emailed statement on Tuesday, referring to the company's subsidiary.
Around 120 km is left to be laid in Danish waters as well as almost 30 km in German waters, before it makes landfall at the northern German coastal town of Lubmin, near Greifswald.
The project has become more politicised after Kremlin critic Alexei Navalny, who was poisoned in August in Siberia and flown to Germany for treatment.
The department said it imposed the sanctions on the Russian pipe-laying ship "Fortuna" and its owner, KVT-RUS, under the Countering America's Adversaries Through Sanctions Act (CAATSA).
Concerned over looming US sanctions targeting companies associated with the project.
Bilfinger had been contracted to develop, deliver and operate process control and safety systems for the controversial pipeline as well as supply a gas-fired heating generation unit.
The consortium will probably be able to say at the end of January or in early February when work will resume, the spokesman said.
The construction of a 2.6-km long portion of the pipeline in Germany's shallow waters was resumed and finished last month with the help of the Fortuna.