WASHINGTON — With President Bush heralding a drop in the poverty rate for the first time in his administration, Democrats are seizing on the rising number of uninsured Americans to renew their efforts to expand government health care programs and move toward universal coverage.

The nation’s poverty rate last year declined significantly for the first time since 2000, while the number of people without health insurance increased by more than 2 million, data released yesterday by the U.S. Census Bureau show.

The percentage of people living in poverty dropped to 12.3%, from 12.6% in 2005. For the second straight year, the nation’s median household income rose, to $48,201, an increase of 0.7%, according to the annual census report.

While the income level has not returned to its prerecession peak of $49,244 in 1999, “the gap is narrowing,” the chief of the Census Bureau’s Housing and Household Economic Statistics Division, David Johnson, said.

Positive trends in income and poverty were tempered by the rise in the number of Americans without health insurance, which stood at a record 47 million in 2006. That represents an increase of 2.2 million people from 2005, or 0.5%. The number of uninsured children increased by 700,000, or 0.8%.

The census report sparked new proposals from Mayor Bloomberg, who appeared in Washington yesterday to champion his efforts to reduce poverty in New York while pushing for an expansion of antipoverty tax credits on the federal level.

The release of the annual data also comes amid a showdown between Congress and the Bush administration over a Democratic proposal to expand the Children’s Health Insurance Program. The bill has support among many Republicans, but the president has threatened to veto it, saying it amounts to a tax increase.

In a presidential campaign in which health care has emerged as a top domestic issue, Democratic candidates were quick to respond to a spike in the number of uninsured Americans.

None were quicker than John Edwards, the former North Carolina senator who has made combating poverty and enacting universal health care centerpieces of his campaign.

“The need for fundamental change in our government is obvious,” Mr. Edwards said in a statement issued shortly after the data became public. “We simply cannot stand by while tens of millions of our fellow citizens go without the necessities of life,” he said. “We need truly universal health care and a national effort to eliminate poverty.”

In statements later in the day, Senator Clinton said the report “demonstrates the urgent need to cover every American,” while Senator Obama of Illinois said that “in the richest nation on Earth, it is a moral outrage that one in 10 American families live in poverty and 47 million Americans do not have health care.”

Mr. Bush, meanwhile, took credit for the drop in the poverty rate. “When we keep taxes low, spending in check, and our economy open — conditions that empower businesses to create new jobs — all Americans benefit,” he said in a statement. The census data, he added, ” confirms that more of our citizens are doing better in this economy.”

Citing the rise in the number of uninsured people, he touted his own health care proposal — virtually ignored by the Democratic Congress — that would alter the tax code in a bid to encourage more Americans to buy private coverage. “What American workers do not need right now are tax increases to fuel excess spending by the Congress,” the president said.

Economic analysts offered tepid praise for the drop in the poverty rate. “Better than the alternative,” a scholar at the American Enterprise Institute, Douglas Besharov, said. He pointed to a “relatively good economy” that has not matched the economy during the 1990s, which saw a steeper decline in poverty. “2006 was a good year,” he said. “It wasn’t a banner year, but it was a good year.”

The poverty rate is used to determine eligibility for an array of federal benefits. For a family of four with two children, it stands at $20,444.

In New York City, the poverty rate ticked up slightly, to 19.2% in 2006 from 19.1% in 2005, in a change that city officials said was not statistically significant.

Addressing the Brookings Institution at the National Press Club, Mr. Bloomberg praised welfare reforms and an expansion of the Earned Income Tax Credit in the 1990s for achieving reductions in the poverty rate. He said that while progress had been made in recent decades, it was far from sufficient. Addressing possible solutions, the mayor — a potential presidential contender — returned to what has become his hallmark as he has traversed the country making speeches in recent months, decrying partisanship and government inaction.

“Are we just going to shrug our shoulder and hope that the market’s invisible hand lifts them up? Or pound our fists and demand that the heavy hand of government pick them up?” he said. “If we’re going to take either route, we are going to fail. I don’t think there’s any if, ands, or buts about it.”

The mayor stumped for what he acknowledged was a “controversial” experiment to offer cash payments to low-income students and families as incentives for work and school attendance and performance.

Broadening his focus to the national level, he proposed eliminating the so-called marriage penalty, changing the way poverty is measured, and expanding and changing the EITC, which he said is the “best anti-poverty tool we have.” At an estimated cost of $8.5 billion, the tax credit expansion would reduce the age of eligibility and raise the maximum qualifying income for individuals without children while also simultaneously penalizing fathers who don’t work or pay child support.