WASHINGTON — President Obama worked Tuesday to sell a sweeping tax cut agreement to skeptical Democrats, arguing that he got the best deal he could from congressional Republicans and vowing to fight them again in two years when it expires.

In so doing, he cast himself squarely in the middle of American politics, lashing out at the GOP for insisting on extending tax cuts for the wealthy, while also ripping liberals who pushed him to reject compromise with Republicans even if it means letting tax cuts for the middle class expire on Dec. 31.

"My number one priority is to do what's right for the American people, for jobs and for economic growth," he said at a hastily called White House news conference.

Obama used the news conference to try to sell the deal to extend the Bush-era tax cuts for two years on all incomes. He'd wanted to make the tax cuts permanent for all incomes of less than $200,000 a year — $250,000 for families — and to let them expire for all incomes above that amount.

But he said that Republicans, with their ability to block any deal in the Senate, opposed any extension unless it included higher incomes.

"It's tempting not to negotiate with hostage takers," he said. "Unless the hostages get harmed.... The hostage was the American people. I was not willing to see them get harmed."

While some liberals urged him to fight on, he said that would have hurt the economy too much, as well as too many individual families, including 2 million Americans whose unemployment benefits also would have run out as a consequence.

"This isn't an abstract debate. This is real money for real people," Obama said.

By forcing the Republicans to accept an extension of jobless benefits for the unemployed, and adding a one-year reduction in the payroll tax, he said the overall package would help the economy.

"It's a good deal for the American people," he said.

"I know there are some who preferred a fight," he added, but said a long fight that risked higher taxes in the short term "might have been good politics. But it would have been bad for the economy."

Instead, he said, he'll fight another day.

"I'm as opposed to the high-end tax cuts as I have been... I will fight to end them," he said. "We're going to keep on having this debate."

Before Obama spoke, liberal Democrats were in an uproar. Rep. Peter Welch, D-Vt., circulated a letter to House Speaker Nancy Pelosi, D-Calif., telling Obama, "Don't back down."

After the news conference, Welch warned that the deal would "empower the Republican leadership to fight every last one of our progressive priorities, arguing that the country can't afford it. Ironically, the president will be proving them right."

Republicans, however, were pleased.

"I think the vast majority of members of the Republican caucus to the U.S. Senate feel that this is a step in the right direction, an important step to take for the American people," said Senate GOP leader Mitch McConnell of Kentucky.

Obama said he simply couldn't win his quest to end tax cuts for the wealthy against unified opposition holding millions hostage against a Jan. 1 deadline.

"On the Republican side, this is their holy grail this seems to be their central economic doctrine," he said. "We can't get my preferred option through the Senate right now."

He said he had to settle now because the tax fight only will get more difficult after Republicans add more seats in January as the result of November's midterm elections.

"It was going to be a protracted battle, and they would have a stronger position next year than they do currently," he said.

He used that argument to explain why he agreed to the Republican demands now — but in so doing also raised the question of how he could do any better in two years when he'll face the same Senate.

That will put the tax debate right in the middle of the 2012 election.

"We will have two years to discuss the budget," he said. "Either they rethink this position, or I think they're not going to do well in 2012."

Even as he tailored his message to centrist voters, Obama dumped the rhetoric of bipartisanship.

He lamented that if he wasn't so committed to the economy and the plight of American households, "I could have enjoyed the battle with the Republicans over the next month or two because... the American people are on our side."

The president also dared Republicans to try to back him into a corner on other policy initiatives, saying that "this is a very unique circumstance" and that "I will be happy to see the Republicans test whether or not I'm itching for a fight on a whole range of issues."