Expanding the state's Medi-Cal program to meet new federal guidelines could add up to $4 billion a year in costs at the same time California is implementing federal health reform, potentially putting its budget "right out of whack," Gov. Jerry Brown said Thursday.

In an interview with The Associated Press, Brown said his administration is seeking federal waivers for some of the proposed expansions to the health care program for the poor. The changes could add more than a million people to the 7.7 million already served under California's version of Medicaid.

"We're very interested in seeing everyone — as many people as possible — covered, but I am very concerned that negotiations in Washington could have huge negative impacts in California by loading billions of dollars of new and unexpected costs that will just take our budget and put it right out of whack," the Democratic governor said.

States must commit to fully expanding coverage for individuals who make up to about $15,400 a year, or about 138 percent of the federal poverty limit, in order to tap more generous funding. California is one of many states that have yet to decide whether to expand their programs.

In California, the proposed change would add between 1 million and 1.4 million people to Medi-Cal. The state is also in the process of moving 900,000 children to Medi-Cal from the health insurance program known as Healthy Families.

"We certainly are going to come out with a program that will chart a path to expand Medi-Cal eligibility, but the federal government has to give us the tools so that we can temper the rising costs in health care," he said.

Brown said adding more people to the rolls goes beyond what the state has available to pay for it "unless we can get waivers and law changes that will allow us to deliver a health care with a more, let's say, judicious, business model."

Medicaid, the federal-state health insurance program for the poor and disabled, is one of two primary ways in which the Affordable Care Act will expand coverage for people who currently have no health insurance. California has been aggressive in setting up its new health insurance exchange, which will make subsidized private health insurance available starting in 2014.

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Associated Press writer Judy Lin contributed to this report.