The European Union warned that it could retaliate against the U.S. “within a matter of days” should the country unilaterally strengthen sanctions against Russia, saying EU-based energy companies risk becoming collateral damage. The European Commission, the bloc’s executive arm, made the threat a day after the U.S. House of Representatives gave the green light to tougher economic penalties against Russia. The draft law now goes to the Senate for approval, which would risk a deeper trans-Atlantic split over economic and security policies. The U.S. measures would prohibit American businesses from being involved in some energy projects that include Russian companies. The EU is concerned about provisions that would let the U.S. president sanction companies working on Russian energy-export pipelines and oblige the Treasury secretary to impose penalties on foreign firms involved in special crude-oil projects in which sanctioned Russian partners hold a 33 percent stake. “The U.S. bill could have unintended unilateral effects that impact the EU’s energy-security interests,” commission President Jean-Claude Juncker said in an emailed statement on Wednesday. “If our concerns are not taken into account sufficiently, we stand ready to act appropriately within a matter of days.” The latest trans-Atlantic tensions follow sharp disagreements over U.S. President Donald Trump’s “America First” agenda, including his protectionist tilt, his withdrawal from an international treaty to fight climate change and his criticism of European defense spending. The fresh friction also contrasts with close cooperation between the EU and former U.S. President Barack Obama over sanctions against Russia for its encroachment in Ukraine. The commission is echoing concerns expressed by German Chancellor Angela Merkel, whose spokesman said in June that the U.S. Congress’s plan for expanded sanctions against Russia posed a threat to European economic interests. One casualty could be the planned $10 billion Nord Stream 2 natural-gas pipeline between Russia and Germany.