Ambassadors from several European countries – including Irish ambassador to the United States Dan Mulhall – have urged US Congress to support the recent decision to lift sanctions on Russian energy giant Rusal, the parent company of Aughinish Alumina in Limerick.

In a letter sent to US House speaker Nancy Pelosi and senate minority leader Chuck Schumer, the ambassadors said that while they recognise the rationale under which Russian oligarchs had been sanctioned by the US, “it is crucial that the sanctions avoid unintended consequences for European companies.”

Aluminum plants “in Austria, France, Germany, Ireland, Italy, Sweden, and the United Kingdom have faced increased prices and significant challenges in maintaining their daily operations” the letter states.

The letter, which was sent last week, was published a day after Democrats grilled treasury secretary Steve Mnuchin about the decision to lift sanctions on companies controlled by Russian oligarch Oleg Deripaska in December.

That decision - which was notified to Congress on December 19th - was warmly welcomed by the Irish government, amid fears that the US clampdown on Rusal could ultimately affect the alumina plant Aughinish which employs hundreds of people.

But Democrats have reacted angrily to the move, accusing the Trump administration of going soft on Russia.

Mr Mnuchin was summoned to appear before Democrats this week on Capitol Hill to explain the decision by the White House.

Speaking after the 90-minute closed door meeting, Mr Mnuchin said he would consider delaying the move to allow members of Congress more time to scrutinise the decision. But he showed no signs that he intended to ultimately change the decision.

Irish officials in Washington have been working closely behind the scenes with European counterparts to lobby the US authorities on the issue, amid fears that the sanctions could severely disrupt the European and global aluminium markets.

In a measure of the resistance to the move by Democrats, Richard Neal, the chair of the Ways and Means committee and a close friend of Ireland on Capitol Hill, was among those who called on Mr Mnuchin to delay the decision. In a letter to the treasury secretary after Thursday’s meeting he noted that the sanction decision had been notified to Congress just before the recess. A delay “would allow Congress a meaningful opportunity to exercise oversight over this proposed action as intended by CAATSA, including through reviews of relevant intelligence assessments,” he wrote, referring to the Countering America’s Adversaries through Sanctions Act.

Ms Pelosi also blasted Mr Mnuchin after the briefing, branding it “one of the worst classified briefings we’ve received from the Trump administration,” despite “stiff competition.”

In a statement after the meeting the Treasury Department highlighted the fact that Deripaska has relinquished control of the company, and pledged to ensure that he complies with those terms.

“These entities are undergoing significant restructuring and governance changes that sever Deripaska’s control and significantly diminish his ownership,” Mr Mnuchin said in the statement. “Treasury will be vigilant in ensuring that EN+ and Rusal meet these commitments. If these companies fail to comply with the terms, they will face very real and swift consequences, including the reimposition of sanctions.”

Though Democrats now control the House of Representatives, Republicans still maintain a majority in the Senate so are likely to still give approval to the move.