WASHINGTON (AP) — President Barack Obama defiantly challenged lawmakers Thursday to vote for his jobs plan or explain why not. "This is not a game," he declared.

In keeping with the sharp new tone the president has adopted against Republicans, he challenged them to support him or spell out what they would do instead to help the economy that's slowed, with unemployment stuck above 9 percent, as the 2012 presidential campaign heats up.

The president said that without his nearly $450 billion package of tax cuts and public works spending there will be fewer jobs and weaker growth. He said the bill could guard against another economic downturn if the situation in debt-laden Europe worsens.

With the plan expected to come up for debate in the Senate next week, he urged every senator to think "long and hard about what's at stake."

"Our economy really needs a jolt right now," Obama said at a White House news conference.

Obama defended his new approach of jettisoning negotiations with Republicans in favor of traveling the country to assail GOP lawmakers, sometimes by name, and trying to rally public support for his plan.

He said he's gone out of his way to work with Republicans and try to find common ground over the past two years.

"Each time, we have seen game playing," the president said. "What I've done over the last several weeks is take the case to the American people so they know what is going on."

Yet Obama's campaign has not swayed Capitol Hill Republicans who oppose the higher taxes he and other Democrats want to use to pay for the proposal. They accuse Obama of playing "campaigner in chief" instead of working with them.

"If the goal is to create jobs, then why are we even talking about tax hikes?" Senate Minority leader Mitch McConnell, R-Ky., said Thursday.

Republicans are resolutely opposed to much of Obama's jobs initiative, both for its tax increases for wealthier people and small businesses and its reprise of stimulus spending on roads, bridges and schools and grants to local governments to pay the salaries of teachers and first responders.

Obama did say he would support a new approach by Senate Democrats for paying for his jobs bill with a tax on millionaires rather than his plan to raise taxes on couples making more than $250,000.

Obama attempted to use Thursday's news conference to increase pressure on his Capitol Hill opponents heading into the first vote on the jobs bill that he proposed a month ago. He has been promoting it around the country ever since, often traveling into swing states or the home states of key Republicans such as House Speaker John Boehner.

"If it turns out that Republicans are opposed to the bill, they need to explain to me, and mostly importantly their constituents, what they would do," Obama said.

Obama said the economy is weaker now than at the beginning of the year. Citing economists' estimates, he said his $447 billion jobs bill would help the economy grow by 2 percent and create 1.9 million jobs.

"At a time when people are having such a hard time, we need to have an approach that is big enough to meet the moment," he said.

Obama addressed the disaffection with politics pervasive among the public that's driven down his approval ratings — and even more so, Congress' — as he seeks a second term.

Clearly frustrated, Obama blamed it on Republicans who he said refuse to cooperate with him even on issues where he said they once agreed with him. He talked about the ugly debate over raising the government's borrowing limit that consumed Capitol Hill and the White House over the summer, until Obama gave in to Republican demands for deep spending cuts without new taxes.

"They don't get a sense that folks in this town are looking for their best interests," Obama said of Americans in general. "So if they see that over and over again, that cynicism is not going to be proven wrong unless Congress does something different."

"What the American people saw is that Congress just didn't care."

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