Washington — With no sign of a breakthrough in budget negotiations on Capitol Hill to reopen the government, the National Park Service announced Sunday it will take the "extraordinary step" of using visitor fees to make sure national parks are operational during the partial shutdown.

"We are taking this extraordinary step to ensure that parks are protected, and that visitors can continue to access parks with limited basic services," the agency's deputy director Daniel Smith said in a statement Sunday.

Under the move, the Park Service will use entrance, camping and parking fees to fund efforts to remove trash, maintain restrooms, deploy rangers and to make more areas accessible to the public in parks across the country. The agency, however, said it will still not be able to fully open parks and that many will remain closed.

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Smith said the Office of the Solicitor at the Department of the Interior was consulted about the proposal before it was unveiled.

The Park Service is part of the Department of the Interior, one of the agencies affected by the prolonged partial government shutdown that began in late December. Negotiations between congressional leaders and the White House continue to be locked in a stalemate over President Trump's unwavering demand for more than $5 billion to construct a "steel barrier" along the U.S.-Mexico border.

Some national parks are closed because of the shutdown, but others remain open with limited services provided by the federal government, states and private organizations. Park visitors, however, have reported many problems during the lapse in funding, including waste buildup. And some visitors have died in parks since the shutdown began.

Democratic lawmakers denounced the unprecedented move by the administration and said it may not pass legal muster. The Federal Lands Recreation Enhancement Act (FLREA) stipulates that fees charged by federal parks are designed to fund services for visitors — not the maintenance of parks.

Incoming chairwoman of the House Appropriations Interior-Environment subcommittee Rep. Betty McCollum, D-Minnesota, suggested the move is likely illegal. "The law is clear: if the federal government is shut down, our National Parks must also be closed to protect public safety and pristine spaces. It is not acceptable to use FLREA funds to keep the parks open, and the Department of the Interior's actions likely violate appropriations law," McCollum, who will soon have oversight over the Interior Department's spending, said in a statement.

Arizona Congressman Raúl Grijalva, the new chairman of House Natural Resources Committee, said his committee will probe whether the administration's action is "legally justified."

"President Trump and his advisers apparently just woke up to the fact that the shutdown they created several weeks ago has done terrible damage to our country. The American people already own our national parks and fund their upkeep," Grijalva wrote Sunday in a statement to CBS News. "The president expects them to either pay more to keep the toilets clean out of their own pockets or pay millions of dollars for his ridiculous wall."

Rebecca Kaplan contributed to this report.