President Obama in the last press conference of his first term drew a hard line over the federal debt limit, saying he would not negotiate with Republicans over an increase in the nation's borrowing capacity and insisting Monday that failure to raise it would delay Social Security benefits and veterans' checks.

The president has long accused Republicans of obstructionism, but his charge Monday that conservatives were holding "a gun at the head of the American people" was his most searing accusation against the GOP over the looming fiscal debate.

"They will not collect a ransom in exchange for not crashing the American economy," Obama said. "The full faith and credit of the United States of America is not a bargaining chip."

The president's East Room appearance was the final press conference of his first term, but it served more as a launching pad for the first salvo of his second-term showdown with Republicans over the debt ceiling, budget deficit and spending cuts.

The White House and Congress must reach a debt ceiling deal by mid-February or the federal government risks default on its obligations and the inability to pay those who depend on government programs like Social Security and Medicare. Yet, the two sides remain far apart on how to proceed.

Republicans were quick to paint the president as out of touch with public sentiment over a ballooning $16.4 trillion national debt.

"The American people do not support raising the debt ceiling without reducing government spending at the same time," said House Speaker John Boehner, R-Ohio.

Added Senate Minority Leader Mitch McConnell, R-Ky., "The president and his allies need to get serious about spending, and the debt limit debate is the perfect time for it."

Republicans were also quick to note that Obama himself voted against raising the debt ceiling when he was a junior senator from Illinois in 2006 -- as did Vice President Biden and Senate Majority Leader Harry Reid, D-Nev.

Republicans on Capitol Hill dismissed the president's tough talk as a bluff, pointing to similar language from the White House in 2011, before Obama ultimately agreed to a compromise with Republicans to raise the debt limit. And after the GOP last month endorsed a "fiscal cliff" deal with virtually no spending cuts, the political price for doing so again is untenable, they said.

The president insists he has no backup plan if Republicans block the debt limit increase and warned that not hiking the borrowing capacity could spur another recession.

Obama sees his re-election as a validation of his policies and negotiations with Congress, but some analysts advised Republicans not to give in to his demands.

"While the congressional Republicans are far from fiscal saints, they are not the biggest problem, and giving Obama his way on the debt limit is the fiscal equivalent of letting an alcoholic alone overnight in a liquor store -- a very bad idea," said Richard Vedder, an economist at Ohio University.

Once the debt ceiling debate concludes, Obama said, he is "open to making modest adjustments to programs like Medicare to protect them for future generations" but that he also wants to close tax deductions and loopholes for the wealthy.