WASHINGTON (Reuters) - The 40-year-old ban on most U.S. crude oil exports will “very likely” be lifted in the government spending bill, and talks on the final budget deal are likely to continue through the weekend, a Senate aide said on Friday.

Trucks and other equipment used in the oil fields are seen at a depot in Dickinson, North Dakota June 26, 2015. REUTERS/Andrew Cullen

The aide did not want to be identified due to the ongoing nature of the talks.

When asked if it was likely that the oil export ban would be lifted, a spokeswoman for Senate Minority Leader Harry Reid, a Nevada Democrat, said there was no final deal yet.

“We do not have a final agreement on the omnibus or tax extenders,” said Reid’s spokeswoman Kristen Orthman.

Leaders in both the House and Senate have been meeting behind closed doors in recent days to see if a deal can be reached on the bill. Energy interests, and Republicans, who lead both chambers of Congress, say lifting the trade restriction would keep the U.S. drilling boom alive and give U.S. allies alternatives to Russia and OPEC for their oil supplies.

Opponents, including many Democrats in the Senate, say it would put oil refining and ship building jobs at risk and more drilling would harm the environment and increase the number of trains carrying crude oil.

The White House has said repeatedly that President Barack Obama opposes legislation in the bill to lift the ban and that Congress should instead work to help green sources of energy. It has stopped short of saying Obama would veto a spending bill that includes lifting the ban.

The Senate aide said Democrats were very likely willing to trade lifting the ban for a multi-year extension of wind and solar tax credits and reauthorization and full funding of the Land and Water Conservation Fund, which maintains national parks with revenues from oil operations.

There were still major disagreements over the funding bill ahead of a deadline on Wednesday on the $1.15 trillion package to fund the government through September, 2016. Many of the disagreements are related to Congress’ response to the recent gun massacres in Paris and California.

On energy matters in the bill, Democrats oppose efforts to block emissions rules by the Environmental Protection Agency or U.S. funding of the UN Green Climate Fund, a major item that is part of ongoing climate talks in Paris.