It was the president's first solo news conference since November.
A number of the questions dealt with Iran's nuclear weapons program and what the United States is prepared to do about it.
Obama said there is a diplomatic "window" that must be tried before considering military action against Iran. Obama also ripped into unnamed Republican candidates who talk about sterner measures against Iran.
"We will not countenance Iran getting a nuclear weapon," the president told reporters. "At this stage it is my belief that we have a window of opportunity that this still can be resolved diplomatically."
Obama said top U.S. and Israeli intelligence officials agree on that assessment. He said Israel, as a sovereign nation, is making its own decisions.
But the president criticized "what's said on the [Republican] campaign trail," without giving specifics or names.
"Those folks [Republican candidates] don't have the responsibility. They aren't the commander in chief. ... This is not a game."
Obama said when reporters ask the unnamed saber-rattling candidates "what they would do," they repeat what he's been doing for the last three years, including sanctions.
"If some of these folks decide that it's time to start a war they should say so and explain it to the American people," Obama said.
Asked to explain why the United States has not used armed forces to intervene in Syria, as NATO did in Libya last year, Obama said, "For us to take military action unilaterally as some have suggested, or to think there's a simple solution, in my view is a mistake."
The president said the United States would continue to work with key Arab states and international partners to resolve the Syrian crisis where the government is waging war on its own people.
Obama also hammered Congress for what he said was a failure to act to help the American economy.
Obama said there has been some economic progress during the last few months.
"But there are still millions of Americans who can't find a job. There are millions more who are having a tough time making the rent or the mortgage, paying for gas or groceries."
Obama said "our job in Washington isn't to sit back and do nothing, and it's certainly not to stand in the way of the recovery. Right now we've got to do everything we can to speed it up. ... Congress did the right thing when they passed part of my jobs plan and prevented a tax hike on 160 million working Americans this year, and that was a good first step. But it's not enough. They can't just stop there and wait for the next election to come around."
The president said Congress should "end tax breaks for companies that are shipping jobs overseas and use that money to reward companies that are creating jobs here in the United States. I've put forward a proposal that does that, and there's no reason why Congress can't come together and start acting on it."
Congress should also vote to raise taxes on the most wealthy "so that we don't have billionaires paying a lower tax rate than their secretaries."
He said Congress also "should pass my proposal to give every responsible homeowner a chance to save an average of $3,000 a year by refinancing their mortgage at historically low rates."
"If Congress refuses to act ... I'll continue to do everything in my power to act without them," the president said.
Without naming him, Obama took a swipe at Republican rival Mitt Romney, who has suggested the housing crisis should play out its course in the marketplace.
"I'm not one of those people who believe that we should just sit by and wait for the housing market to hit bottom," Obama said.
Obama touched briefly on gasoline prices, saying as he has in the past, "There is no silver bullet." He said the energy crisis requires a number of approaches, including conservation and cleaner energy.
Obama also said radio personality Rush Limbaugh's epithets targeting a Georgetown law student "have no place in the public discourse." On his radio program, Limbaugh called the student a "slut" and a "prostitute" for testifying before a congressional panel about what she felt was the need for contraception coverage in insurance.
The president said he called the student, Sandra Fluke, to say her parents should be proud of her.
"I thought about [daughters] Malia and Sasha, and one of the things I want them to do as they get older is to engage in issues they care about," Obama said. "Even ones I may not agree with them on. I want them to be able to speak their mind. ... And I don't want them attacked or ... called horrible names because they're being good citizens."
Obama also drew laughter when he wished Republican rival Romney "good luck."
Asked to respond to Romney's statement that Obama was "the most feckless president since Jimmy Carter," the president paused and said, "Good luck tonight. No, really."
The White House has insisted Obama's news conference was not meant to rain on the Republican Super Tuesday parade. Republicans held contests in 10 states Tuesday.