The Environmental Protection Agency's plan to give states more time to comply with its proposed carbon emissions limits for power plants isn't enough, say critics of the forthcoming rule.

While opponents of President Obama's signature climate change policy said they would reserve full judgment until the rule is finalized, which is expected next week, an apparent two-year delay to the regulation doesn't address the substantive concerns they have.

"We'll see. We've got to take a look. I think that the regulation itself is a problem. I think, again, we're right back into a federal one-size-fits-all and the administration imposing something that Congress refused to do," Sen. John Hoeven, R-N.D., told reporters.

A source familiar with the final rule told the Washington Examiner on Wednesday that states wouldn't need to begin cutting electricity-sector emissions until 2022, compared with 2020 in the proposed rule. The source also said the EPA would incentivize states to act early on adding clean energy and energy efficiency measures beginning in 2020.

The rule likely will maintain the proposed target of slashing nationwide electricity emissions 30 percent below 2005 levels by 2030. The source also said the rule would be "stronger" than what was proposed.

One industry source said that keeping the original target date while knocking back the compliance deadline by two years actually shortens the amount of time states have to shift their electricity systems. The source added that EPA's offering of incentives to begin making changes as early as 2020 suggested states might need all the time they can get.

"It you need to act early in order to comply within the eight-year period of time then it makes it a fictitious argument that you don't have to comply until 2022," the source told the Examiner.

But Sen. Ed Markey, D-Mass., said his staff had been briefed on the clean energy provision and said that it was designed so that "those states that move fastest and earlier get bigger rewards."

"And so the overall goal of reducing greenhouse gases remains intact, and they've just built in additional flexibility that I think at the end of the day is still going to get the job done," Markey told reporters.

Rob Sargent, energy program director with Environment America, added in a conference call, "If this helps states avoid doing a lazy way out and just add a gas plant or two, then we're all for it."

Many states said the proposal's 2020 targets amounted to a "regulatory cliff" because it required them to achieve most of their reductions by that deadline. Those states worried they would have to take large quantities of coal-fired power offline and wouldn't have enough new power sources ready as replacements.

Pushing back the beginning of the compliance period by two years attempts to address that. A slide the EPA hosted on its website, which was obtained by E&E Publishing, showed that the agency plans to give states until September 2016 to submit an initial plan and until September 2018 to file a final plan for the EPA to approve, rather than the original target dates of June 30, 2016, and June 30, 2017.

The changes might win over a few states whose concerns about the rule were purely about timing, said Jeff Holmstead, a lawyer who represents energy clients for Bracewell & Giuliani. But states that have taken a more hard-line approach that the regulation itself is illegal wouldn't be swayed, he said.

"I don't think you'll see any governors backing away from challenging the rule, and I still think the rule probably will not pass muster in the courts. But if I'm wrong and the courts do uphold the rule, then these changes provide a more reasonable timeline for implementing the rule," Holmstead, who was the EPA air chief under former President George W. Bush, said in an email.

A number of governors have hinted they won't comply with the rule if it isn't significantly changed in the final version. Republican Oklahoma Gov. Mary Fallin has signed an executive order forbidding compliance. Those governors contend the rule will raise energy costs and have raised questions about its legality, saying the EPA is overstepping its authority by calling on emissions reductions outside of individual power plants.

"Extending deadlines is nothing more than window-dressing and wouldn't change the fact that the Clean Power Plan is unlawful and threatens the reliability and affordability of power across the country," GOP Oklahoma Attorney Scott Pruitt, who is suing the EPA over the rule, said in an emailed statement.

Representatives for Republican governors Scott Walker of Wisconsin and Mike Pence of Indiana, both of whom have threatened not to comply with the rule, told the Examiner that they would wait until the regulation is finalized before commenting.

"Governor Pence has told the EPA that the rule must be demonstrably and significantly improved. We'll wait until the rule is final to determine whether the EPA listened," spokeswoman Bridget Cleveland said in an email.