President Barack Obama delivers remarks about the fiscal cliff negotiations in the Eisenhower Executive Office Building next to the White House December 31, 2012 in Washington, DC. Obama said he was hopeful that an agreement could be found to avert the fiscal cliff in Congress, which is closing in on a deal that would raise taxes on households that make more than $450,000 a year and individuals who make more than $400,000. (Photo by Chip Somodevilla/Getty Images)

An agreement in principle to avert broad tax increases and spending cuts appeared imminent Monday night.

A senior Democratic source told NBC News that an accord had been reached. A senior GOP source said it “looks good” and that the outcome in the Senate would be clearer after Vice President Joe Biden conferred with Senate Democrats. Biden arrived at the Capitol to meet with Democratic senators Monday night.

Although a Senate vote later Monday night was possible, it’s not clear how an accord would fare in the House.

The interim New Year’s Eve tax deal negotiated by Biden and Senate Republican Leader Sen. Mitch McConnell of Kentucky would raise income taxes on single earners with annual incomes above $400,000 and married couples with incomes above $450,000.

As of mid-afternoon Monday, the sticking point involved the “sequester,” the cuts to spending – about $100 billion to start in 2013 — that were mandated by the Budget Control Act which President Barack Obama signed into law last year. Republicans have signaled they might let the sequester take effect unless it was offset by other spending cuts; the GOP has also said it might accept a delay, but only for a few months.

The Obama administration, however, is pushing for a longer delay in implementing the sequester. Otherwise, the president said, replacing those automatic cuts must be “balanced” — shorthand for a combination of new taxes and other spending cuts.

Obama tried to push talks over the finish line earlier in the afternoon with a statement from the White House.

“Today, it appears that an agreement to prevent this New Year’s tax hike is within sight,” the president said at the White House. “But it’s not done.”

In the absence of a broader agreement to resolve the sequester, McConnell appeared in the Senate floor to request a vote only on the tax element of the fiscal cliff.

“Let’s pass the tax relief portion now,” he said. “Let’s take what’s been agreed to and keep moving.”

But it’s not clear that Democrats, who were led in negotiations by Vice President Joe Biden, would agree to de-link the tax debate from other fights over the sequester and extending expiring unemployment benefits past Dec. 31.

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