Federal agencies engaged in the energy sector will experience little immediate impact if the U.S. government undergoes a partial shutdown after Dec. 21.

But a prolonged shutdown could have bigger consequences, such as postponing court deadlines in cases where the U.S. Environmental Protection Agency is a defendant and halting some permitting activities for energy production in federal areas.

Funding for about 25% of the federal government, including the EPA and U.S. Interior Department, runs out Dec. 21. Congress already authorized spending for most other federal agencies, such as the Department of Energy and the Federal Energy Regulatory Commission, for the current fiscal year, which runs through September 2019.

The U.S. Senate passed a continuing resolution Dec. 19 that would extend current funding levels for the EPA and other agencies through Feb. 8. But the U.S. House of Representatives moved to attach more money to build a wall along the U.S.-Mexico border, a key priority of President Donald Trump but a proposal that likely will not clear the Senate.

The clash over border wall funding therefore has raised the chances that the federal government will undergo a partial shutdown in the coming days. If that happens, EPA Acting Administrator Andrew Wheeler said his agency has "sufficient carryover funds to operate for a limited period of time."

Wheeler said the EPA will remain open the week of Dec. 24 in the event of a shutdown, with all employees to follow their planned schedules for the week, including the holidays Dec. 24-25 for Christmas. If the shutdown lasts beyond Dec. 28, Wheeler said the EPA will provide further updates on its operating status.

In a Dec. 17 contingency plan, the EPA said it would only perform certain exempted or excepted activities during a funding hiatus. Those activities include work on Superfund sites necessary to avoid an imminent threat to human life; securing EPA national laboratories; and response programs for environmental emergencies such as a chemical spill.

But the Environmental Protection Network, a group of former EPA officials and staff, said a shutdown still would suspend most EPA enforcement and Superfund cleanup activities and halt issuance of federal permits, although states may issue permits that do not require support from the EPA or another federal agency. In addition, courts may accept a shutdown as a reason to postpone hearings or extend other deadlines in cases where the EPA is a defendant, the network said.

Interior did not respond to inquiries regarding what it will do in the event of a shutdown, but the department's website contains contingency plans for its various bureaus.

The agency's Bureau of Land Management, which oversees leasing of federal lands for energy production, said in a March contingency plan that a shutdown would cease most BLM activities "with the exception of law enforcement, emergency response functions, and operations necessary for the safety of human life or the protection of property." Administrative and regulatory work on the Trans-Alaska crude oil pipeline would be exempted, however.

Interior's Bureau of Ocean Energy Management, which oversees energy development on the U.S. Outer Continental Shelf, will continue to assist in safety and environmental enforcement permitting activities in those areas and process and review certain revisions to ongoing permitting work. But the bureau will not process or review new exploration and development plans during a shutdown, the agency said in a December contingency plan.