Reid and other Senate Democrats say House Republicans must accept that agreement will require support from legislators in both parties, rather than a GOP majority in the House pushing through a measure on its own.

He insisted that a Senate-passed plan with Obama's $250,000 threshold would pass the House if Boehner would allow a vote. However, the Senate proposal is held up on constitutional grounds, because legislation that increases revenue must originate in the House.

Boehner and Republicans complain the Senate has refused to take up any proposals they have passed in the past two years. Reid argues that the GOP measures amount to a conservative wish list of unacceptable spending cuts and reforms intended to shrink government and weaken entitlement programs vital to senior citizens, the poor and the disabled.

Some House Republicans have said they would join Democrats in supporting the president's proposal in hopes of moving past the volatile issue to focus on the spending cuts and entitlement reforms they seek.

The possibility of a fiscal cliff was set in motion over the past two years as a way to force action on mounting government debt.

Now, legislators risk looking politically cynical by seeking to weaken the measures enacted to try to force them to confront tough questions regarding deficit reduction, such as reforms to popular entitlement programs such as Social Security, Medicare and Medicaid.

The two sides seemingly had made progress early last week on forging a $2 trillion deficit reduction deal that included new revenue sought by Obama and spending cuts and entitlement changes desired by Boehner.

Obama's latest offer set $400,000 as the income threshold for a tax rate increase, up from his original plan of $250,000. It also included a new formula for the consumer price index applied to some entitlement benefits, much to the chagrin of liberals.

Called chained CPI, the new formula includes assumptions on consumer habits in response to rising prices, such as seeking cheaper alternatives, and would result in smaller benefit increases in future years.

Statistics supplied by opponents say the change would mean Social Security recipients would get $6,000 less in benefits over the first 15 years of chained CPI.

Liberal groups sought to mount a pressure campaign against including the chained CPI after news emerged this week that Obama was willing to include it, calling the plan a betrayal of senior citizens who had contributed throughout their lives for their benefits.

For his part, Boehner conceded on increased tax revenue, including higher rates on top income brackets and eliminating some deductions and loopholes.