Republicans and Democrats have only four days to attain conformity before hundreds of billions of dollars of tax rises and expenditure cuts take consequence. Over time the loss of income would have a harmful consequence on the US economy. Analysts say descending over the "cliff" could tip the US into depression and set back the global financial improvement.
The priority for Democrats is preserving tax cuts for households earning less than $400,000 (£250,000) while hoist taxes for the richest 2% of Americans in order to rein in shortage expenditure.
Republican congressmen feel they were re-elected with a permission to block new taxes - positively for those earning less than $1m. They are also challenging cuts in some accepted healthcare and benefit advantage schemes.
Divisions in the two chambers of assembly - with Republicans having a popular in the House of legislature while Democrats control the commission - are also making it hard to reach agreement: Any feasible deal must pass votes in both cavity and be signed by the president.
A substitute plan planned by Republican Speaker John Boehner - which would have seen taxes rise only on those receive over $1m - failed in the House of legislature late last week. The autonomous popular leader in the Senate, Harry Reid, said his consideration an agreement was improbable and Senate Republican leader Mitch McConnell said his generation was unwilling to sign a blank cheque.