It is very silly to assume that US would have said they will continue the deal even if India conducts Nuclear tests. Every country looks for their own interests and India has to make the best use of this deal. No one else will do it for them. * KEY PASSAGES IN PREAMBLE OF AGREEMENT
"An essential basis of India's concurrence to accept Agency safeguards ... is the conclusion of international cooperation arrangements creating the necessary conditions for India to obtain ... reliable, uninterrupted and continuous access to fuel supplies from companies in several nations, as well as support for an Indian effort to develop a strategic reserve of nuclear fuel to guard against any disruption of supply...
"India may take corrective measures to ensure uninterrupted operation of its civilian nuclear reactors in the event of disruption of foreign fuel supplies."