A law firm that previously employed President Donald Trump s interior secretary has, for several years, represented Saudi Arabia, the petroleum-rich nation that recently launched an oil price war that could bankrupt U.S. fossil fuel producers.

The government of Saudi Arabia has paid lobbying giant Brownstein Hyatt Farber Schreck more than $4 million since 2016 to represent its interests in Washington, D.C. Last year, the Colorado-based firm received $1.5 million from the Saudi government for professional services, according to its January regulatory filing to the Department of Justice.

The revelation comes as Trump has personally waded into the oil dispute, tweeting Thursday that he has asked de facto Saudi ruler Crown Prince Mohammed bin Salman to work with Russia, another top energy producer, to curb oil production so prices can rise again.

Interior Secretary David Bernhardt was an attorney and shareholder at BHFS before joining the Trump administration in August 2017, lobbying on behalf of oil, gas and mining interests that are now benefiting from the administrations aggressive environmental rollbacks. The lobbying giants domestic clients include oil and gas interests that have been hit hard by the oil market crash.

BHFS hasnt been shy about its access to Trumps team. In a memo to clients the day after Trump was elected, the firm wrote that it has significant relationships across both chambers and party leadership, as well as those who will steer the incoming Trump administration.

The firm also boasted that Politico named Marc Lampkin , managing partner of BHFSs Washington, D.C. office, a need to know K Street Power Player inside the Trump transition and that other members of our team have also been active advisors to the Trump transition team.

Lampkin is one of several BHFS employees who have lobbied on the Saudi governments behalf, according to DOJ filings .