The European Union (EU) is ready to act "within a matter of days" if it felt the new US sanctions against Russia undermined the bloc's energy security, the European Commission (EC) said on Wednesday.
"If our concerns are not taken into account sufficiently, we stand ready to act appropriately within a matter of days. America first cannot mean that Europe's interests come last," EC President Jean-Claude Juncker said.
The sanctions against Russia, Iran, and North Korea were approved in a landslide on Tuesday by the US House of Representatives.
The bill also bars US President Donald Trump from easing sanctions on Moscow without Congress' approval.
Sanctions could target EU firms
Brussels fears the new sanctions will damage European firms and oil and gas projects on which the EU is dependent.
The Commission said a number of EU concerns had been taken into account in the most recent version of the bill, but said it could lead to sanctions on any company, including European, that worked on Russian energy export pipelines.
"The US bill could have unintended unilateral effects that impact the EU's energy security interests," Juncker said, adding that there should be unity among Western allies on sanctions.
To date, anti-Russia sanctions have been coordinated on both sides of the Atlantic in a common Western front, reminiscent of the Cold War.
Depending on its implementation, the Commission observed, this could affect infrastructure transporting energy resources to Europe. An example would be the maintenance and upgrade of pipelines in Russia that feed the Ukraine gas transit system.
"It could also have an impact on projects crucial to the EU's diversification objectives such as the Baltic Liquefied Natural Gas project," the EC said in a statement.
An EU document prepared for the commissioners also laid out the EU's plans to seek "demonstrable reassurances" that the White House would not use the bill to target the bloc's interests.
The new sanctions target the disputed Nord Stream 2 project for a new pipeline running from Russia to Germany under the Baltic Sea. But the EU note says, "The impact would, in reality, be much wider."
The EC said that it plans to file a complaint at the World Trade Organization if diplomacy fails.
A German economic committee said on Thursday that the option of European counter-sanctions must be kept open as "a very last option" if the US sanctions hit companies in Germany.
The Committee on East European Economic Relations revised upward to 20 percent its forecast for growth in German exports to Russia this year, from 10 percent growth expected previously.
On Thursday, Germany's economy minister Brigitte Zypries said that the new sanctions could harm German companies and add another difficulty to Berlin's relationship with Washington.
"The US has left the common line it had with Europe for sanctions against Russia," Zypries said, adding that by not coordinating with Europe on the matter, there was a risk that German companies would be harmed.
Sanctions at odds with international law
France's foreign ministry on Wednesday said the new US sanctions against Iran, Russia, and North Korea appeared at odds with international law due to their extra-territorial reach.
French and European laws would need to be adjusted in response and added that discussions would be necessary at the EU level because of the potential impact on European citizens and firms, the foreign ministry said in a statement.
Russia and Iran vow response
Russia said that the new US sanctions against Moscow would take already battered ties into uncharted waters.
"The attitude to this (law) will be formed on the basis of a thorough analysis, and the decision (on how to respond) will certainly be taken by the head of state, President Putin," said Kremlin spokesman Dmitry Peskov.
Iran will reciprocate if the US imposes new sanctions on it, President Hassan Rouhani said on Wednesday.
"We will also take any other steps we deem necessary for the development of our country and the prosperity of our country, regardless of their (US) sanctions and their policies, we will pursue our path," Rouhani said.