Editing Impossibility of performance (section)

==United States==
At common law, for the defence of "impossibility" to be raised performance must not merely be difficult or unexpectedly costly for one party, there must be no way for it to actually be accomplished. However, in the United States it is beginning to be recognized that "impossibility" under this doctrine can also exist when the contemplated performance can be done but only at an excessive and unreasonable cost, i.e., commercial impracticability.<ref>See, e.g., {{cite court |litigants=Transatlantic Financing Corp. v. United States |vol=363 |reporter=F.2d |opinion=312 |pinpoint= |court=[[United States Court of Appeals for the District of Columbia Circuit|D.C. Cir.]] |date=1966 |url=https://law.justia.com/cases/federal/appellate-courts/F2/363/312/264117/ |accessdate=2018-07-23 |quote=}}</ref>  On the other hand, some US sources see "impossibility" and [[impracticability]] as being related but separate defences.