The Environmental Protection Agency will give states more time to begin cutting carbon emissions from power plants, according to a source familiar with the final regulation.

Under the final Clean Power Plan rule, which is expected to be released as early as next week, enforcement of the regulation would begin in 2022, rather than the proposed 2020 start date. The changes outlined by the source are an attempt to quash concerns that states would need to shift their power sectors too quickly, imposing potentially heavy costs and creating concerns about maintaining adequate electricity supply.

The regulation is the centerpiece of President Obama's climate change agenda, but it has faced intense criticism from Republicans, the energy industry and a handful of state governors who say the rule would raise power costs and put coal-mining companies out of business. Opponents also have contended the EPA's timeline is unworkable.

"You're going to see a final rule that is in many ways stronger than the proposed rule, but at the same time gives states the flexibility they need," the source said.

Senate Majority Leader Mitch McConnell, R-Ky., has encouraged state governors to refrain from submitting compliance plans to the EPA. A few governors have signaled they would follow that advice if the proposed rule isn't changed. But whether the adjustments, first reported by the New York Times and the Washington Post, are enough remains to be seen.

The rule is expected to maintain a 2030 target for slashing electricity emissions nationwide 30 percent compared with 2005 levels. That means that while states won't have to begin complying until 2022 under the potential change in the final rule, they will have to reconfigure their power systems by the same end date.

Still, the alterations go to the heart of one of the biggest issues states had with the proposal. The draft version required some of the steepest emissions cuts to go into effect beginning in 2020, and some states were concerned it would force widespread shuttering of coal-fired power plants without any new power to replace it.

On top of that, even states that support the overall aim of the regulation were upset that they wouldn't get credit for action to reduce emissions that occurred before enforcement began in 2020. But another change to the proposal would aim to address some of those qualms.

The final rule will incentivize states that begin adding renewable energy and energy efficiency measures in 2020. Those changes would be counted as if they had occurred after 2022, when states must begin complying with the rule.

Despite the changes to the rule, states and affected industries are expected to sue the EPA soon after its release. They contend that the final rule won't substantively change any of the legal questions that opponents have raised, such as whether the EPA has the authority to order emissions cuts beyond those made at individual power plants.