WASHINGTON, Dec. 16, 2009 -- President Obama pushed back against critics, including the former head of the Democratic Party, who have said that the health care bill in the Senate is fatally flawed and should be scrapped altogether.

In an interview with ABC News' Charles Gibson, the president said he laid out for Congress specific things he wanted to see in the health care legislation -- including providing insurance for millions of uninsured and not driving up the deficit -- and that the current bill still has those benefits.

"Now, if you can tell me that those things are not worth it, then you and I have a very different opinion about what the task is here," he said.

But Dr. Howard Dean, former Democratic National Committee chairman and a medical doctor, charged this week that the Senate bill has been so watered down that it is no longer worth supporting.

There are some good elements in the current health care bill, Dean said Wednesday on "Good Morning America," but "at this point, the bill does more harm than good."

Nevertheless, Obama expressed confidence today that the legislation will ultimately pass, but he indicated that it may not provide immediate results and it may be several years before the American people see real progress in health care.

"If I can say at the end of my first term that, you know what, we are poised to deliver on the promise of health care after the legislation has passed, I think that'll be important," he said.

The president stressed that failure to act on health care would be dire. If Congress does not pass legislation that will bring down the spiraling costs of health care, the federal government "will go bankrupt," Obama told Gibson.

"If we don't pass it, here's the guarantee: ... Your premiums will go up, your employers are going to load up more costs on you," he said. "Potentially, they're going to drop your coverage, because they just can't afford an increase of 25 percent, 30 percent in terms of the costs of providing health care to employees each and every year."

The costs of Medicare and Medicaid are on an "unsustainable" trajectory, Obama said, and if there is no action taken to bring them down, "the federal government will go bankrupt."

"This actually provides us the best chance of starting to bend the cost curve on the government expenditures in Medicare and Medicaid," Obama said.

Obama told Gibson that anybody who says they are concerned about the rising deficit or worried about tax increases in the future has to support this health care bill.

"Because if we don't do this, nobody argues with the fact that health care costs are going to consume the entire federal budget," the president said.

Obama reiterated what he told Senate Democrats behind closed doors last week: "This will be the single most important piece of domestic legislation that's passed since Social Security."

When asked whether he felt that individual senators, such as Sen. Joe Lieberman, I-Conn., were holding him hostage on the health care legislation, the president first put the blame on Republicans.

"I think that what we have right now in the Senate is a situation where the opposition party has made a political decision that we are going to say no to everything, we're going to not be at the table, we're going to just not get involved," he said.

But he acknowledged that he needed all 58 Democrats and two independents to be on board with the bill the Senate ultimately votes on if it has any hope of passing.

"Every single one of them," Obama said.

When pushed by Gibson on the heel dragging by individual senators, Obama would only say of his former colleagues, "Each of them have very strong opinions."

Obama is facing an increasingly skeptical American public when it comes to his push for health care reform.

The latest ABC News/Washington Post poll found that support for the health care reform package, while never robust, is now at a low ebb and opposition has been steadily growing stronger in intensity.

For the first time, a majority of those surveyed disapproved of the president's work on health care (53 percent) and opposed the health care reform package making its way through Congress (51 percent, compared to 44 percent approval).

That seven-point margin for opposition is its most to date -- statistically significant for the first time -- and the differential in intensity of sentiment has grown since September.

Obama: Seeing Costs of War 'Hits You Like a Ton of Bricks'

Obama also faced criticism over the length of his deliberations on determining a new strategy for Afghanistan. He ultimately decided to send 30,000 more American troops there starting early next year.

He told Gibson that his mindset changed from the beginning of the process to his final decision.

"I think that there is a sobriety that overcomes you during the course of a decision like this that that's hard to describe," Obama said. "With this one, you feel it viscerally. You lose sleep. You think about families. You think about history. You walk through Arlington. You're reminded of the image of a mother in the rain sitting in front of a tombstone."

Obama foresaw the decision to send American men and women into combat as "being difficult" but said nothing compared to being in the actual midst of that decision-making process.

"When you meet with families and you talk to soldiers who've come home disabled as a consequence of their service, the sheer emotional force of that I think is something that you can't anticipate," he said. "It's something that hits you like a ton of bricks."

Obama said the most powerful moment of his first year in office was his overnight trip to Dover Air Force Base in Delaware, where he met with families who had just lost loved ones in Afghanistan and observed a "solemn dignified transfer movement," the event that marks the return to the U.S. of the remains of fallen service members.

"Walking up the ramp of the transport plane by myself and seeing those caskets, it's indescribable, and it reminds you of the extraordinary courage and sacrifice that these young men and women are willing to make," the president said. "But it also reminds you that you have the solemn obligation to make the best possible decision that you can make and that there is an element of tragedy involved in war that is inevitable.

"If you think that this is all chest-beating and glory," he added, "then you're probably not making the best decision as possible."

Obama indicated that while he has outlined a timeline for withdrawal in Afghanistan, enacting that plan will depend on progress made in reversing the Taliban's momentum there.

Obama said that if the new surge of American troops does not work, then "additional decisions" will have to be made "based on what the situation on the ground is."

"What we did, I think, was find that point where, having built up Afghan capacity, we're then in a position to start reducing our presence because we've built up a partner in the region that can work with us effectively," he said.

But Obama acknowledged that there are no guarantees that the strategy will work "perfectly" and said that no matter what success the U.S. sees in Afghanistan, there will still be problems with governance there and the challenges dealing with the Taliban and al Qaeda.

He said that if he were to only serve one term in office, he wants to hand off to the next president a more stable Afghanistan that does not require a "a perpetual occupation" by the U.S. military.

Obama Says Time May Come When He Forces Congress to Drop Earmarks

With the national debt now at a record $12 trillion, Obama soon will receive from Congress a spending bill that has more than 5,000 earmarks, pet projects for members, that will cost taxpayers nearly $4 billion.

Obama has pledged to reform the earmark process, but the White House has said he will not veto this bill when it gets to his desk.

Gibson asked him how he could sign the bill and at the same time claim to be serious about deficit reduction.

Obama said that raising taxes or cutting government spending next year would be wrong with the economy still "very fragile" and coming out of a recession, but his administration has to find ways to bring down the deficit in the mid- and long-term.

But when pressed by Gibson on why he would not just force Congress to drop the earmarks on this spending bill, Obama said, "There may come a point fairly soon in which we have to take that approach."

But he noted that changing the culture on Capitol Hill will not happen overnight.

"I mean, this is part of the challenge of democracy, is that, you know, I have to deal with 535 members of Congress of both parties who may in the abstract say, 'We hate government waste and government spending,' but when it comes to that project in their district, they think it's absolutely vital," the president said. "And so we are trying to change a culture here."