Continued from page 1

For their part, Republicans said Mr. Obama lost credibility by changing his stance on private insurance plans.

“It is very disturbing that the president refused to stand by his promise that Americans would be able to keep their doctor and health care plan if they wanted to,” said Rep. Dave Camp of Michigan, the top Republican on the House Ways and Means Committee, which will help write a health care bill.

He said that by allowing companies to drop coverage, Mr. Obama is “caving in” to Democrats in Congress who are pushing for more government control.

After a quick start with the stimulus program, Mr. Obama’s legislative agenda has bogged down as polls show Americans wary of the amount of spending and of expanded government control.

Originally scheduled for the White House’s Rose Garden, the news conference was moved inside to the James S. Brady Press Briefing Room because of the heat and humidity.

The president used the 55-minute-long event to press for action on curbing greenhouse-gas emissions through a market-based carbon-emissions permit system, saying the costs will fall largely on polluters.

The president stuck to what appeared to be an optimistic Democratic message that downplays the bill’s costly requirements to force reductions in carbon-dioxide emissions. The president called them “incentives that will spur the development of new sources of energy.” He also stressed that the bill would produce savings on energy costs and create domestic jobs.

Mr. Obama also found himself on the defensive on several fronts, including his response to Iran’s elections. Asked how he responded to congressional critics, such as Sen. John McCain, Arizona Republican, Mr. Obama said he’s got a broader responsibility.

“Only I’m the president of the United States. And I’ve got responsibilities in making certain that we are continually advancing our national security interests and that we are not used as a tool to be exploited by other countries,” he said.

Among the sharper exchanges was Mr. Obama’s rebuke to a reporter from the McClatchy Newspapers chain. The reporter asked whether the president still smokes regularly, saying it was of interest because Mr. Obama signed a bill into law this week imposing hefty regulations on tobacco companies.

He said he is “95 percent cured” of his habit, though he said, “There are times where I mess up.”

He said he doesn’t smoke in front of his children.