New rules limiting emissions from U.S. power plants that are expected to be proposed on Friday will “provide certainty” to the coal industry, environment and energy chiefs told lawmakers anxious about the fuel’s future.

“We believe coal will continue to represent a significant portion of the energy supply in the decades to come,” Environmental Protection Agency administrator Gina McCarthy told the House of Representatives Committee on Energy and Commerce on Wednesday.

McCarthy’s testimony, her first since being confirmed to the EPA post in July, came two days before the agency is due to unveil the first major rule of the Obama administration’s new climate change action plan.

The EPA is expected to release a new version of a proposal it was due to finalize in April to set greenhouse gas emissions limits for future fossil fuel power plants.

Republicans and some Democrats in energy-producing states say President Obama has launched a war on coal with a new climate plan.

Obama outlined his climate plan in June, saying the United States would target its largest source of emissions—power plants, which account for nearly 40 percent of greenhouse gases.

McCarthy and Energy Secretary Ernest Moniz testified before the House panel, which in calling the hearing said it wanted to examine the administration’s previous and future climate regulations that it says have cost $22 billion this year.

Several other federal agencies were invited to the hearing but declined to provide a witness, including the Department of Agriculture and the Department of the Interior.

McCarthy parried several lawmakers who questioned whether the EPA has the authority to propose rules that could effectively prevent the construction of new coal plants in the United States by making compliance with tighter emissions standards impossible.

She said technology that is being developed to capture carbon from power plants and store the emissions or use them to recover oil was “feasible.”

“On the basis of information that we see out in the market today and what is being contemplated, CCS [carbon capture and storage] is technically feasible and is available today,” McCarthy said.

Four CCS projects now in development are moving closer to operating at commercial scale, McCarthy added.

Moniz, a longtime advocate of developing cleaner coal technology, said several types of carbon capture projects—in power production and industrial processes—are adding to the economy.

“The components are all there,” he said.

The current viability of carbon capture and storage technology is likely to be central to the debate around the upcoming rule.

Opponents of EPA regulation of carbon dioxide emissions argue that until the technology is truly available on a commercial scale, the EPA cannot justify setting strict emission limits for new coal-fired power plants.

“In the clean air debate, the technology was available. In the greenhouse gas debate, it is not available. That is really the number one concern that we have,” said Congressman John Shimkus, a Republican from Illinois.