On the heels of criticism over his 2012 federal budget proposal, from both the left and right, President Obama joined the fray in a Tuesday morning news conference where he defended his choices.

The president notably responded to the impression that his budget, with its focus on small domestic programs, puts too much on the backs of the poorest Americans. Echoing the rationale provided earlier by members of his administration, he first explained the reasoning behind certain unpopular cuts, like the Pell Grant and LIHEAP funding.

He continued that his budget adds dollars to other areas to help the vulnerable, such as restoring funds that had been cut from food stamps (SNAP), allocating more money to public school districts, backing science and technology programs to bring underrepresented students to those fields, and boosting infrastructure spending.

“Sometimes I'm just frustrated by the number of people out there who are struggling, and you want to help every single one individually,” he said, when asked if he really understands the pain of cash-strapped Americans. “You almost feel like you want to be a case worker and just start picking up the phone and advocating for each of these people who are working hard, trying to do right by their families.

“But my job is to make sure that we’re focused over the long term: Where is it that we need to go? And the most important thing I can do as president is make sure that we’re living within our means, getting a budget that is sustainable, investing in the future and growing the economy. If I do that, then that’s probably the most help I can give to the most number of people.”

Another common critique on the budget is that it makes no mention of Medicare, Medicaid and Social Security, despite those being the biggest long-term drivers of the deficit. The president said that those are negotiations he’ll be making with Congress over the next few months.

“I said in the State of the Union and I'll repeat, that side of the ledger only accounts for about 12 percent of our budget,” he said. “So we've got a whole bunch of other stuff that we're going to have to do, including dealing with entitlements.”

Obama took care to mention, however, that he doesn’t want to significantly tamper with Social Security, which he described as being less of a deficit-driver than the other two.

The president also addressed the fact that his budget ignores most of the proposals offered by his bipartisan fiscal commission, which put sacred-cow expenditures, like tax breaks for homeowners and military spending, on the chopping block. Yet, going by Obama’s budget, it’s almost like the commission never existed.

He pointed out that the report was also so divisive that it couldn’t get the required 14 votes from the full 18-member commission. One person who notably passed from signing on was the chairman of the House Republican budgeters.

“He’s got a little bit of juice when it comes to trying to get an eventual budget done,” Obama said, repeating that he’ll have to work with both sides to arrive at something with a viable chance of passing. “I mean, my goal here is to actually solve the problem. It’s not to get a good headline on the first day.”

The presser’s recurring theme of both parties working together is a hopeful one, but Obama’s actual negotiations with Republicans are sure to be rife with conflict. His budget is just the opening bid for that drawn-out process.

As many reservations as I may have with the president’s proposal – namely its trimming of relatively small social programs over, say, seriously addressing the Pentagon’s massive budget – it beats the ideas that Republicans have put forth. They haven’t unveiled a 2012 budget yet, but the GOP vision for financing the rest of this year includes far bigger reductions to Pell Grants, heating assistance and CDBG funding, plus cutbacks in the WIC nutritional assistance program for low-income mothers.

On the matter of forthcoming budget negotiations, Obama said he knows it will be prickly but feels confident that both sides can navigate the situation together.

“I expect that all sides will have to do a little bit of posturing on television and speak to their constituencies, and rally the troops and so forth,” he said. “But ultimately, what we need is a reasonable, responsible, and, probably, somewhat quiet and toned-down conversation about where can we compromise and get something done.”