An expected presidential veto of a bill that would boost spending on a children's health insurance program could leave hundreds of thousands of California children without coverage, health experts say.

The result would be disastrous for California, said Anthony Wright, executive director of Health Access California, a nonprofit organization that advocates for affordable health care. Without additional funding for the program next year, as many as 250,000 California children could be dropped, he said.

The federal government's State Children's Health Insurance Program, or SCHIP, provides low-cost health coverage for about 6.6 million children nationwide.

More than 831,000 children from working families statewide are covered by the program, known in California as Healthy Families. More than 53,000 children in the central San Joaquin Valley are enrolled.

The children are from families who cannot afford private insurance but earn too much for Medi-Cal, the state's insurance program for the poor. In California, children are eligible in families with earnings of up to 250% of the federal poverty level, or about $52,000 a year for a family of four.

The program expires Sunday, but state officials said they expect Congress to provide money to continue services at current levels though the end of November.

The worry is that flat funding could continue well beyond that -- even as the cost of health care rises and the number of eligible children grows.

Without extra federal money, "we will have to look seriously at disenrolling children next year," said Amy Palmer, associate secretary for external affairs at the California Health and Human Services Agency.

President Bush has vowed to veto a bill approved Thursday by the Senate and earlier in the month by the House that would give the children's insurance program $60 billion nationwide over the next five years, an increase of about $35 billion. The increase would have covered an additional 4 million of the nation's 9 million uninsured children.

The president has said the increase is too costly. He has proposed giving the program $30 billion, an increase of $5 billion.

California officials say the president's proposed $30 billion would not be enough for California to sustain its program.

"That just doesn't cut the mustard for California, and it doesn't cut the mustard for most of the states in the country," said Lesley Cummings, executive director of the Managed Risk Medical Insurance Board, which oversees California's Healthy Families program.

Without adequate funding, "we're going to have to look at options for cutting back the program," Cummings said.

California was counting on federal funds of $6.7 billion to $8.1 billion over the next five years to maintain the program. The bill approved in Congress would provide that. The program cost about $1.1 billion this year.

The state had hoped for even more so that eligibility requirements could be loosened.

About 763,000 California children were without insurance in 2005, according to California Health Interview Survey conducted by the University of California at Los Angeles. Of that number, about 200,000 were eligible for Healthy Families but were not enrolled.

State officials also could be scrambling to rewrite the governor's health-reform plan if the Healthy Families budget remains flat, said Wright of Health Access.

"It means health-care reform is going to be tougher," Wright said. "We have to raise money from other places -- raise more dollars in-state."