President Barack Obama is considering a possible budget concession on Social Security cost-of-living increases after House Speaker John Boehner dropped his opposition to raising tax rates for some top earners, said two people familiar with the talks.

Obama and Boehner met for about 45 minutes at the White House today with two weeks remaining to avert more than $600 billion in spending cuts and tax increases set to start in January. Treasury Secretary Timothy Geithner also attended the meeting, according to a Treasury Department statement. Obama is seeking an income-tax rate increase for top earners while Boehner wants to cut spending on entitlement programs.

Senate Majority Leader Harry Reid, a Nevada Democrat, said today it appears the chamber will need to reconvene Dec. 26 to work on the budget.

Switching the inflation yardstick to the so-called chained consumer price index would reduce Social Security cost-of-living benefit increases and generate fresh revenue because it also would reset income-tax brackets. Some Democrats in Congress have said they’re willing to make that change.

“We want to preserve these programs for the long run,” Democratic Senator Tom Carper of Delaware said last week. “We need a great compromise; Democrats need to compromise on entitlement reform that doesn’t savage older people or poor people.”

‘Tough Choices’

White House spokesman Jay Carney said, “I’m not going to get into specific policy proposals,” when asked about using chained CPI. He added that Obama is “prepared to make tough choices.”

Still, Reid has declared Social Security off the table in any deal to avert the so-called fiscal cliff of tax increases and spending cuts.

Other Democratic leaders including Senator Dick Durbin of Illinois haven’t ruled out the idea, without endorsing it. Obama also didn’t close the door in an interview earlier this month with Bloomberg News.

The key for Democrats is whether a change can be made in a way that would protect low-income and other vulnerable groups of senior citizens, said the two people familiar with the talks, who spoke on condition of anonymity to discuss the negotiations.