The European Union has expressed concern about US plans to impose fresh sanctions on Russia, amid concern they could hurt energy companies.
The EU Commission sounded the alarm after the US House of Representatives voted in favour of the measures, despite opposition from Donald Trump.
The bill is likely to complicate the US president's hopes of improving relations with Russia.
It aims to punish Russia for alleged interference in the 2016 US election.
In a statement, the Commission President Jean-Claude Juncker said: "The EU is fully committed to the Russia sanctions regime."
But he warned of "unintended unilateral effects that impact the EU's energy security interests".
Several European nations, including Germany, are angry because the new law could penalise companies working on pipelines from Russia, for example by limiting their access to US banks.
The legislation, which also includes sanctions against Iran and North Korea over ballistic missile tests, still needs to be passed through the US Senate before it can be sent on to the president to be signed.
It is unclear whether the president will veto it.
What concerns the White House is a measure that limits the president's traditional right to waive the sanctions, instead forcing him to consult Congress first, says the BBC's state department correspondent Barbara Plett-Usher.
The broad bipartisan support the legislation attracted in the House shows just how wary lawmakers are about Mr Trump's pro-Moscow approach, she adds.
Russia's relationship with the president has dogged his first six months in office, amid allegations Moscow interfered to help Mr Trump get elected.