President Obama, who four years ago pledged to bridge Washington's political divide, sounded a very different note in his second inaugural address Monday, warning Congress that he intends to do battle over partisan issues like climate change, gay marriage and gun control.

"Parts of it sounded like a campaign speech," Sen. Rob Portman, R-Ohio, said of Obama's address.

Inauguration Day served as a pause for the president and lawmakers between a bruising 2012 election and the looming battle over taxes and spending. Indeed, the president's first act after renewing his oath of office was to dine with Republicans inside the Capitol while a string quartet played Mozart and Capitol staff served grilled bison and apple pie a la mode.

House Speaker John Boehner, R-Ohio, even talked of "the spirit of harmony" as he presented Obama with the flag that was flying over the Capitol during his swearing-in.

But as they left the lunch, Republicans barely concealed their disappointment with the president and what they saw as partisan, divisive speech that will further strain already tense relations between the White House and Capitol Hill.

That disappointment was compounded when the president appeared to take a shot at one top Republican, House Budget Committee Chairman Paul Ryan, the 2012 running mate of Republican Mitt Romney. Obama insisted that America is "not a nation of takers," as the Republicans suggested during the campaign. Ryan, R-Wis., repeatedly declined to comment on Obama's remark.

Republicans said they were shocked that Obama barely mention the nation's financial problems during his 15-minute speech.

Senate Minority Leader Mitch McConnell, R-Ky., had called on Obama to use the inaugural speech to lay out a plan for dealing with massive budget deficits, but Obama didn't even mention the nation's $16.4 trillion debt.

Instead, Obama laid out an agenda designed to appeal to his most liberal supporters and one that sets up fights with Republicans over immigration, gun control and climate change.

"My disappointment in the speech," Portman said, "was that I think the president missed an opportunity to talk about a place were we can find common ground."

Rather than talk about the need to reform entitlement programs like Social Security and Medicare, the biggest drivers of the nation's debt, the president praised those programs and dismissed Republican claims during the campaign that Americans are too dependent on government.

"These things do not sap our initiative," Obama said of the entitlement programs Republicans want to remake. "They strengthen us."

House Natural Resources Committee Chairman Doc Hastings, who would oversee any debate over climate change, said he wasn't surprised by the president's partisan tone just four years after Obama ran on a promise to end the partisan bickering in Washington.

"After all," Hastings, R-Wash., said, "he got re-elected on a left-wing agenda so it only stands to reason his inaugural speech would be on the left."

Still, Obama left the luncheon on a conciliatory note, telling lawmakers that despite their "profound difference" agreement was possible.

"I'm confident that we can act at this moment in a way that makes a difference for our children and our children's children," Obama said.