Amid a budget debate that will affect the health care of virtually every family, a new poll finds support for President Obama's overhaul at its lowest level since passage last year.

The Associated Press-GfK poll showed that support for Obama's expansion of health insurance coverage has slipped to 35 percent, while opposition stands at 45 percent and another 17 percent are neutral. That nearly ties the previous low in September 2009, when after a summer of heated town hall meetings dominated by critics, only 34 percent supported Obama's approach.

The worry this time appears to be federal budget deficits driven by unmanageable health care costs. Among seniors, whose views are critical in any debate over health care, support for the law dipped below 30 percent for the first time in AP-GfK polling.

Obama delivered a major speech Wednesday laying out his path for reducing deficits. While administration officials have acknowledged the need for more savings from Medicare and Medicaid, congressional Republicans have offered a bold alternative to tackle health care costs.

House Budget Chairman Paul Ryan, R-Wis., is proposing to convert Medicare into a "premium support" program. Instead of traditional Medicare, people now 54 and younger would get a fixed payment, or voucher, from the government to buy private health insurance when they retire. Medicaid, which serves low-income people, would be turned over to the states as a block grant program. Taken together, the programs serve about 100 million Americans.

In a ringing defense of Obama's policies, Medicare chief Donald Berwick pleaded Tuesday for more time on the health care law, and branded a leading Republican plan "unfair and harmful" and "a form of withholding care."

Berwick, who oversees Medicare and Medicaid as well as the rollout of the new health care law, told Associated Press reporters and editors Tuesday that the Republican approach would set back efforts to improve quality and squeeze waste.

It would be like "giving people a sum of money and saying, 'Good luck, God bless you,"' Berwick said during an hour-long interview. "That's not about improving care. That's about shifting burdens."

Ryan says his plan will save Medicare from bankruptcy, and market competition will bring down costs without compromising quality.

A pediatrician, Berwick is well-known in the medical community as an advocate for better quality. But in Washington, he has become one of the most controversial administration figures. His statements as an academic praising the British health care system brought him under suspicion from Republicans, who accused him of favoring rationing. Despite his denials, Berwick's confirmation has been blocked in the Senate, and he may have to leave the job by the end of this year.

The political uncertainty didn't stop him from a full defense of the new health care law. He lamented that the administration has not been able to convince the public that the complex legislation will improve quality and reduce costs over time.

They are in a "psychological trap, where nothing looks good," he said. "The public's smart. They're going to wait for the results before they actually change their minds."

If anything, Berwick said, he wished "the tempo of the law were faster," so that Americans could experience the benefits of coverage for virtually all residents and payment changes to reward doctors and hospitals for quality care, not the volume of tests and procedures.

"We are not going to take your care away. We are going to make it better," Berwick said. "The public will notice as we make health care better, but that takes time."

On Tuesday, the Obama administration began a national program to improve safety in hospitals, which are rife with infections and opportunities for medical mistakes.

The new Partnership for Patients will help hospitals adopt proven strategies to reduce those problems dramatically, with the goal of preventing nearly 2 million patient injuries and saving more than 60,000 lives over the next three years. If it works, it could save Medicare $10 billion over that period.

The poll showed the administration's message isn't getting through, particularly with seniors.

Fifty-nine percent of seniors oppose the new health care law, while only 29 percent support it. Disapproval of Obama's handling of health care among seniors has ticked upward to 62 percent, while Republicans are more trusted than Democrats to handle the issue, by a 51 percent to 36 percent margin.

By contrast, among adults of all ages, Obama's approval rating on health care stands at 52 percent, and 53 percent say they trust Democrats to do a better job.

The Associated Press-GfK Poll was conducted March 24-28 by GfK Roper Public Affairs and Corporate Communications. It involved landline and cell phone interviews with 1,001 adults nationwide, and has a margin of sampling error of plus or minus 4.2 percentage points.