Contaminated water from mine sites can flow into rivers and other waterways, harming aquatic life and threatening drinking water supplies. Companies in the past avoided cleanup costs in many cases by declaring bankruptcy.

Newly sworn-in EPA Administrator Scott Pruitt, a longtime critic of the agency during his previous position as Oklahoma attorney general, said the four-month delay would give more opportunity for public comment.

The financial assurance rule was proposed during the Obama administration and fiercely opposed by mining industry representatives, who contended it was unnecessary and redundant because of other programs meant to prevent mines from becoming government cleanup liabilities.

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“By extending this comment period, we are demonstrating that we are listening to miners, owners and operators all across America and to all parties interested in this important rule,” Pruitt said in a statement.

Environmentalists generally endorsed the proposal as a way to make sure mining companies were held accountable. “It appears the new EPA administrator is already favoring industry over public interest with this delay,” said Bonnie Gestring with the advocacy group Earthworks.

The delayed rule was unveiled late last year under a court order that requires it to be finalized by December 2017. The order came after environmental groups sued the government to enforce a long-ignored provision in the 1980 federal Superfund law.

EPA officials said Friday they still intend to meet the court-ordered deadline.

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The proposal would apply to hard-rock mining, which includes mines for precious metals, copper, iron, lead and other ores. It would cover thousands of mines and processing facilities in 38 states, requiring their owners to set aside sufficient money to pay for future clean ups.

From 2010 to 2014, the EPA spent $1.1 billion on cleanup work at abandoned hard-rock mining and processing sites across the U.S.

Companies would face a combined $7.1 billion financial obligation under the proposed rule, costing them up to $171 million annually, according to the EPA. The agency said the amount could be covered through third parties such as surety bonds or self-insured corporate guarantees.

Republican U.S. Senators John Barrasso of Wyoming and Dean Heller of Nevada welcomed Friday’s delay. Barrasso has said the benefits of the proposal were dwarfed by its potential costs to industry. Heller criticized the previous administration for having been “too quick to hand down harsh regulations and rules without considering the impact.”

Last year, an EPA cleanup team triggered a 3-million gallon spill of contaminated water from Colorado’s inactive Gold King mine. The accident tainted rivers in three states with heavy metals including arsenic and lead and highlighted the problem posed by tens of thousands of mine sites across the nation.