Fiscal strains should not prevent the United States from investing in clean energy, education and infrastructure, U.S. President Barack Obama said Wednesday.

Speaking at Northern Virginia Community College, Obama said it was "unacceptable" that so many people remain out of work in the United States, where the unemployment rate rose to 9.1 percent last month.

"We are in a tough fight, we've been in a tough fight over the past 2-1/2 years to deal with a crippling recession," he said, describing a need to spend more on research, technology, roads, bridges and manufacturing facilities to create jobs and bolster the economy.

"We could decide, in solving our fiscal problems, that we can't afford to make any of these investments, and those of us who have done very well don't have to pay any more taxes in order to fund these investments," Obama said.

"But I want to make clear: that is not our history. That's not who we are. I don't accept that future for the United States of America," he said.

Concerns about the U.S. economy's fragility have dragged down some of the president's approval ratings, although recent polls vary widely on voter support for Obama in 2012 elections as compared with potential Republican challengers.

A Washington Post-ABC News poll published on Tuesday showed Obama in a dead heat with Republican candidate Mitt Romney among registered voters.

But a Reuters-IPSOS poll released on Wednesday showed that Obama retains a big lead over potential Republican candidates, including a 13 percentage-point lead over Romney. The poll of 1,132 adults included 948 registered voters.

The unemployment data released on Friday showed the first decline in factory jobs since October. But the White House stressed that over a longer time period, the manufacturing sector has been an engine for U.S. recovery, creating 230,000 jobs since the start of 2010.

The Democratic president has been trying to show that his policies -- including a big economic stimulus package, the auto and financial sector bailouts and a tax-cut deal reached last year -- have stabilized an economy in freefall and have put it on the path to full recovery.

Many Americans remain concerned about the budget deficit, which is expected to hit $1.4 trillion this year, and financial markets are awaiting a congressional deal to raise the limit on U.S. borrowing authority.

The Fitch ratings agency said Wednesday that a failure to raise the debt ceiling could have ratings implications for the United States and warned a U.S. default would threaten both U.S. and global financial stability.

Obama did not address the Fitch warning in his remarks to the community college.