Oil and natural gas development in a portion of the Arctic National Wildlife Refuge (ANWR) moved one step closer to reality late Thursday, after the Senate rejected an amendment to block drilling in the refuge before passing a $4 trillion federal budget for fiscal year (FY) 2018.

The Senate rejected, on a 52-48 vote, an amendment introduced by Sen. Maria Cantwell (D-WA) on Wednesday. The amendment called for striking a requirement that energy committees in Congress find ways to save at least $1 billion over the next decade.

Senate Republicans, led by Sen. Lisa Murkowski (R-AK), chairman of the Senate Energy and Natural Resources Committee, hope to use the requirement as a means to eventually open the 1.5-million acre coastal plain portion of the 19-million acre ANWR, a region also known as the 1002 Area, to energy development.

Cantwell, the committee’s ranking member, was instrumental in blocking similar GOP efforts to open the 1002 Area to development more than 10 years ago, but her latest effort fell short along mostly partisan lines late Thursday. Sen. Susan Collins (R-ME) and the Senate’s two independents voted in favor of the amendment, while Sen. Joe Manchin (D-WV) was opposed.

The Senate then proceeded to pass the budget bill, House Concurrent Resolution 71. It also passed along mostly partisan lines, 51-49, with Sen. Rand Paul (R-KY) joining every Democrat and independent in opposition.

“This budget resolution offers a tremendous opportunity to secure the future of Alaska, from long overdue federal tax reform to responsible energy development in a small part of the non-wilderness 1002 Area,” Murkowski said after the vote. “Tonight was just the first step, but we are now on a path that will allow us to create jobs, generate new wealth, keep energy affordable, and protect our national security.”

Both the Senate and House energy committees now face a Nov. 13 deadline to “submit changes in laws within [their] jurisdiction to reduce the deficit” with their respective budget committees.

With the bill’s passage, Republicans are clear to proceed with plans to enact $1.5 trillion in comprehensive tax reform. But leaders in the Senate and the House of Representatives must first resolve differences between the version of the budget bill that passed the Senate on Thursday and one that cleared the House earlier this month.

The Senate voted 51-48 on Thursday in favor of an amendment by sponsored by Sen. Mike Enzi (R-WY), chairman of the Senate Budget Committee, to expedite the budget reconciliation process. A statement posted onto Enzi’s website Thursday said the House “is expected to work with the Senate to come to an agreement on a joint concurrent budget resolution.”

On Friday, House Budget Committee Chairman Diane Black (R-TN) added “the budget process is not easy, but I am pleased that the final [Senate] version included some changes that reflect many ideas offered in our plan and also has the support of President Trump. In the House, I look forward to swift passage and to working with the president on tax reform, to provide relief to all Americans.”

A coalition of environmental groups — including the Alaska Wilderness League, the Center for Biological Diversity, Earthjustice, the Natural Resources Defense Council and the Sierra Club — vowed to continue their opposition to opening up ANWR to energy development.

“Today’s vote was just the beginning of a long fight to ensure that this Congress does not authorize oil and gas development in the iconic ANWR,” the coalition said. “With the strong support of the American public, we will fight at every step to ensure that this shortsighted provision is not a part of any final budget reconciliation package. There is no reason why Congress should hijack the budget with a controversial rider to drill in the Arctic refuge.”

According to the U.S. Geological Survey (USGS), the portions of the 1002 Area controlled by the federal government hold an estimated 7.7 billion bbl of technically recoverable oil. The USGS estimate climbs to 10.4 billion bbl with the inclusion of Native lands and adjacent state-controlled water areas within a three-mile offshore boundary.