The sanctions that we put in place helped make this opportunity possible. But let me be clear: if this Congress sends me a new sanctions bill now that threatens to derail these talks, I will veto it. For the sake of our national security, we must give diplomacy a chance to succeed. If Iran's leaders do not seize this opportunity, then I will be the first to call for more sanctions, and stand ready to exercise all options to make sure Iran does not build a nuclear weapon. But if Iran's leaders do seize the chance, then Iran could take an important step to rejoin the community of nations, and we will have resolved one of the leading security challenges of our time without the risks of war.