Nearly two-thirds of Americans would be less likely to visit a national park if its fees increased, a new poll finds.

The poll, commissioned by the Outdoor Alliance For Kids, found that 64 percent of respondents would be less likely to visit parks with higher fees, while 68 percent oppose the Trump administration’s proposed fee hikes.

The findings are meant to push back against the National Park Service’s proposal, floated in October, to increase entrance fees at 17 of the system’s most popular parks.

During their peak periods, some parks would charge $70 per car if the hikes were instituted.

Outdoor Alliance For Kids opposes the increases. It commissioned a bipartisan pair of polling firms for the project.

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“This fee hike will reverse years of progress at the National Park Service to make our parks more inclusive and welcoming to kids and families of all backgrounds,” Jackie Ostfeld, the group’s founder, said in a statement.

“If the administration goes through with its proposal to more than double park entry fees, visiting places like the Grand Canyon and Yellowstone will be off the table for many kids and families.”

The proposal has hit significant pushback from Democrats and conservationists, who say it would put many parks out of reach for a significant number of visitors.

Interior Secretary Ryan Zinke Ryan Keith ZinkeTrump extends Florida offshore drilling pause, expands it to Georgia, South Carolina Conspicuous by their absence from the Republican Convention Trump flails as audience dwindles and ratings plummet MORE has defended the proposal as reasonable and necessary to pay for park upkeep and called criticisms “baloney.”

Friday is the deadline for the public to submit comments on the fee increase proposal.

The Outdoor Alliance For Kids poll of 1,000 adults nationwide was conducted by Hart Research Associates and Chesapeake Beach Consulting between Dec. 13 and 17 and has a margin of error of 3.1 percentage points.