[A] continuing sense of reliance and security that the promised performance will be forthcoming. . . is an important feature of the bargain-so states Comment 1 to section 2-609 of the Uniform Commercial Code. At common law, one party to a contract might suffer considerable and justifiable anxiety about the other party's willingness or ability to perform and yet have no legal basis for cancelling the contract or for procuring additional assurances from the other party. Section 251 of the Restatement (Second) of Contracts is designed to provide a remedy for one party's reasonable fears that the other party to a contract will not perform. In certain circumstances the section allows one party to demand assurances of performance from the other and if the other fails to provide adequate assurances, to treat that failure as a repudiation of the contract.
White, James J. "Eight Cases and Section 251." Cornell L. Rev. 67 (1982): 841-60.