A behind-the-scenes battle is underway on Capitol Hill pitting skeptics of Russia against a potential Donald Trump administration and the oil industry, which has massive business interests there.

Trump’s apparent coziness with Russia and its president, Vladimir Putin, has alarmed both Democrats and Republicans. Trump said, for example, that he would consider lifting the sanctions Obama placed on Russia after it annexed Crimea and used force in east Ukraine.

Now a bill is quietly making its way through Congress that would stymie a future president from easing up on Russia. And the battle offers a glimpse at an industry that appears to be quietly laying the groundwork for a Trump administration.

Trump wasn’t yet the Republican nominee when the bill, called the Stand for Ukraine Act, was introduced, in April. But House members are now motivated to pass the legislation in order to stop a potential Trump administration from lifting sanctions, according to two staffers working for representatives who shaped the legislation and are on the House Foreign Affairs Committee, which passed the bill in July. The staffers agreed to speak on background so they could talk freely.

Because President Obama sanctioned Russia through a series of executive orders in 2014, the measures — which stop certain Russian individuals and businesses close to Putin from traveling to the US or doing business with American companies — could easily be undone by a future president. The bill would make that much harder, allowing a president to remove certain sanctions against Russia if and only if Putin gives up Crimea.

Now energy companies appear to have won an early fight to weaken the legislation. The US–Russia Business Council, a trade association of about 150 businesses and other organizations, including oil industry giants ExxonMobil and Chevron, told BuzzFeed News it has asked lawmakers not to make the sanctions against Russia permanent. And in documents filed in late July, ExxonMobil itself disclosed plans to lobby on the bill.

At stake for ExxonMobil is a massive $500 billion deal with Rosneft, a state-owned Russian oil company, to drill for oil in the Russian Arctic.

In September 2014, only two months after the Department of the Treasury put Rosneft on the sanctions list, the two companies announced that they had discovered about 1 billion barrels of oil and oil equivalent off the Russian coast. With the sanctions, ExxonMobil was forced to wind down the well.

The discovery was just a fraction of the 85 billion barrels of oil and oil equivalent the two firms said in 2012 they expected to find at spots offshore, made more accessible by the decline of Arctic sea ice as temperatures rise globally. The Russian company needed ExxonMobil’s expertise in offshore Arctic drilling in order to get to the oil and gas.

As of the end of 2015, ExxonMobil had lost at most $1 billion due to the sanctions against Russia, according to paperwork it filed with the Securities and Exchange Commission.

ExxonMobil is still seeking new inroads into Russia. In June, CEO Rex Tillerson visited Moscow for an investors’ summit he had skipped for the previous two years after the Ukraine crisis, Reuters reported.