The Obama administration structured the Iran nuclear deal to cover up Iranian violations, which may make it impossible to rigorously enforce the landmark agreement as Trump administration officials have suggested, according to a top Republican senator.

The comments from Texas senator Ted Cruz come amid White House debate over how to approach the agreement, which Trump described on the campaign trail as “the worst deal ever negotiated,” as well as congressional moves to impose non-nuclear sanctions against Tehran for ballistic missile development, terrorism, and human rights violations.