Senate Democrats said Tuesday they aim to block their GOP colleagues from passing a 2018 budget that includes a provision to open up the Arctic National Wildlife Refuge to oil and natural gas drilling.

The budget resolution contains instructions for the Senate Energy and Natural Resources Committee to recommend policies to save $1 billion over the next decade, likely to be served by drilling in the refuge, a longstanding Republican goal.

"Tucked inside the Republican budget is a poison pill, one more massive corporate handout, a giveaway of the Arctic Refuge to Big Oil," said Sen. Ed Markey, D-Mass., in a press conference Tuesday. "This is nothing more than a Big Oil polar payout. This heartless budgetary scam underscores the backward priorities of President Trump and congressional Republicans."

Markey said Democrats intend this week to introduce an amendment to remove the drilling proposal from the budget.

Republicans in Congress have long pressed to allow energy exploration in a 1.5 million-acre section of the Alaskan refuge, where billions of barrels of oil lie beneath the refuge's coastal plain.

Congress designated the 19 million-acre Arctic National as a wildlife refuge in 1980, but set aside a 1.5 million-acre section known as the "1002 area" for future drilling if lawmakers approved it.

Democrats have managed to block those efforts for decades. The Republican-controlled Congress in 1995 passed a budget allowing refuge drilling, but the measure was vetoed by former President Bill Clinton.

Opponents of drilling in the refuge warn the chances of success in Congress are better now.

The Senate is primed to use the process of reconciliation to pass its budget blueprint so that it can be approved by a simple majority, requiring 50 votes, rather than the 60 votes needed to overcome a Democratic filibuster.

The House this month passed its 2018 budget resolution, which contains instructions for the House Natural Resources Committee to approve legislation to reduce the government's deficit by $5 billion over 10 years, expected to be filled by allowing drilling in the wildlife refuge.

The Trump administration supports drilling in the refuge, meaning there is little threat of a presidential veto. Last month, the Interior Department lifted restrictions on seismic studies to probe how much oil is under the refuge.

"We know our public lands are under assault," said Sen. Maria Cantwell of Washington, the top Democrat on the Energy and Natural Resources Committee. "Now they are going to try to open up the most beautiful, pristine wildlife refuge we have in the United States of America. There is a reason for 40 years we have protected it. We will not fail this time."

It's not clear if enough Senate Republicans would back the proposal for it to pass.

If all Democrats oppose the budget, just two Republican no votes could derail it, with Vice President Mike Pence breaking a 50-50 tie.

Sen. John McCain, R-Ariz., a moderate who has previously voted against drilling in the refuge, told reporters Tuesday he's undecided about this year's proposal.

The Senate on Tuesday voted 50-47 to begin debate on the 2018 budget. Tuesday's vote initiates roughly two days of debate on the Senate floor and a marathon session, known as a vote-a-rama, before senators can take a final vote on the budget, likely at the end of the week.

Democrats could introduce their amendment on blocking drilling in the wildlife refuge during that session.

"We are working with colleagues to determine the right moment in this budget process to make this amendment, but we are going to do so," Markey said. "It should be a bipartisan issue and we are working hard to advance that goal. This budget scheme should be removed from the budget and put on ice. We will fight it on the Senate floor."