President Barack Obama speaks to the media after meeting with House Speaker John Boehner at the White House, March 1, 2013 in Washington, DC. (Photo by Mark Wilson/Getty Images) (Mark Wilson/Getty Images)

Delivering a scathing civics lesson to House Republicans on Friday, President Obama showed that he's determined to face off against them in the budget battle on his own terms .

As the federal government edges closer to a shutdown, the president chose to make his case directly to the American people rather than engage in direct negotiations with congressional leaders.

Obama ruled out making any concessions on the spending plan -- including rolling back the Affordable Care Act or adopting other items on a laundry list of GOP legislative priorities -- in order to keep the government open or to avert a default on the national debt. He said that though he would be willing to negotiate over items including changes to his signature health care law, "we’re not going to do this under the threat of blowing up the entire economy."

"That’s not how our constitutional system is designed," Obama said during an afternoon briefing at the White House. "We’re not going to do it."

And even as he spoke about the ongoing domestic standoff with Republicans, Obama made it clear he would forge ahead with foreign policy priorities. He said he had spoken by phone to Iranian President Hassan Rouhani on Friday afternoon about reaching an accord on Iran's nuclear program.

"While there will surely be important obstacles to moving forward and success is by no means guaranteed, I believe we can reach a comprehensive solution," Obama said of relations with Iran. "Now, we're mindful of all the challenges ahead. The very fact that this was the first communications between an American and Iranian president since 1979 underscores the deep mistrust between our countries, but it also indicates the prospect of moving beyond that difficult history. I do believe that there is a basis for a resolution."

The contrasting images -- Obama telling Congress to do its job, while seizing the opportunity to perhaps strike a historic nuclear deal with Iran -- hinted at the direction of his presidency in a second term.

With Republicans all but certain to oppose the vast majority of his initiatives -- and even make it difficult for him to keep the government operating -- the president sees the promise of foreign policy achievements all the more compelling. Obama also said he was pleased with progress at the United Nations on work to dismantle Syria's chemical weapons program.

In his remarks on the debt ceiling standoff, Obama argued that negotiating over whether to raise the nation's borrowing limit would set a precedent not just for him "but for future presidents. That’s why we’ve got to break this cycle."

The president described his political opponents in unusually harsh terms, at one point calling them "extremists" who are threatening "to burn the house down just because you haven’t gotten 100 percent of your way."

"That's not how our democracy works," he said.

He also suggested that "the House Republicans are so concerned with appeasing the tea party" they would risk disastrous economic consequences that the country and its citizens could not afford.