WASHINGTON — The final version of President Obama’s signature climate change policy is expected to extend an earlier timeline for states to significantly cut planet-warming pollution from power plants, according to people familiar with the plan.

If enacted, the climate change plan, the final version of which is expected to be unveiled as early as Monday, could stand as the most significant action ever taken by an American president to curb global warming. But some environmental groups have cautioned that a later deadline for states to comply could make it tougher for the United States to meet Mr. Obama’s climate change pledges on the world stage.

The plan consists of three major environmental regulations, which combined are intended to drastically cut emissions of greenhouse gases. The rules take aim at coal-fired power plants, the largest source of greenhouse emissions, and are intended to spur a transformation of the nation’s power sector from fossil fuels to renewable sources such as wind and solar. Under the rules, the Environmental Protection Agency would require states to draft plans to lower emissions from power plants. The agency is also expected to issue its own model of a state-level plan, to be imposed on states that refuse to draft their own plans.

The final rules would extend the timeline for states and electric utilities to comply, compared with a draft proposal put forth by the E.P.A. in June last year, according to people who are familiar with the plan but who spoke on the condition of anonymity because they were not authorized to speak publicly about it.