While Democratic leaders say they are confident they will have the 218 votes needed to pass major health care legislation this weekend, a number of House Democrats, including several from Republican-leaning districts in the South, have announced that they will oppose the measure, which is President Obama’s top domestic priority.

The Democrats currently control 257 voters in the House, and one more Democrat, Bill Owens, newly elected from New York, will be sworn in on Friday. With all 177 Republicans likely to oppose the health care bill, Democrats at most can afford to lose 40 of their own caucus members.

They will definitely lose a bunch. Among them is Representative Ike Skelton of Missouri, chairman of the Armed Services Committee.

“I oppose the creation of a government-run public insurance program and continue to have serious concerns about its unintended consequence for Missourians who have private insurance plans they like,” he said in a statement issued this week.

Mr. Skelton also expressed concerns that the bill would allow tax dollars to pay for abortions, a worry that led 40 Democrats to send a letter to House leaders urging them to tighten provisions to prevent federal money from paying to terminate pregnancies.

Representative Artur Davis of Alabama, who is running for governor there, said he preferred the Senate Finance Committee health bill and would vote against the House version.

“Because we risk disaster if we get this wrong, I will vote no on the health legislation and continue to root for a final bill that fixes the holes in our health care system and contains soaring costs in both the private and public sectors” he said in a statement.

Mr. Davis said he preferred the Senate Finance Committee approach to paying for the bill by imposing a tax on high-cost “Cadillac” health insurance policies, and he also preferred the committee’s decision not to require companies to insure their workers but instead would ask companies to share the cost of subsidizing insurance.

Representative Travis Childers of Mississippi said that he would oppose the House health care bill because it was simply too expensive at a time of economic crisis for the nation.

“First and foremost, I cannot vote for legislation with this big of a price tag in today’s economic climate,” Mr. Childers said in a statement. “I would also like to see legislation that contains stronger language to prohibit federal funding for abortion and provides equal access to care for individuals in rural communities. My concerns in these areas have not been sufficiently addressed by this legislation.”

Representative Bart Gordon of Tennessee announced his opposition in a statement on Thursday. “I can’t support it as it stands now,” he said. “I am concerned about a mandated government-run public option, and I do not like this bill’s financial impact on the state of Tennessee. The Congressional Budget Office has also indicated that the House bill will not reduce the federal government’s spending on health care over the long term — something I believe is essential.”

Representative Jim Marshall of Georgia announced his opposition in an op-ed piece in The Atlanta Journal Constitution on Monday.

“Instead of maintaining the status quo or moving toward a single-payer health care system, we should begin a migration to a health care system with millions of single payers, one in which most patients are the payers,” Mr. Marshall wrote. “Unfortunately, the present House and Senate bills miss the opportunity to begin this critical migration. That’s why I oppose them.”

Other House Democrats expected to oppose the health care bill include Dan Boren of Oklahoma, Bobby Bright of Alabama, Collin Peterson of Minnesota and Gene Taylor of Mississippi.

In addition, other lawmakers are waiting for the outcome of negotiations over the abortion provisions, and still others are concerned about provisions dealing with legal and illegal immigrants.

Some undecided lawmakers said they had been the subject of intense lobbying by members of the Democratic leadership. And Mr. Obama will visit the Capitol to meet with the entire House Democratic caucus on Friday morning to make one last personal appeal for lawmakers’ support.