WASHINGTON—A split between Senate Democrats threatens to derail a U.S.-brokered deal to enable Sudan establish a stable civilian authorities and solve terror victims’ claims against the former routine of Omar al-Bashir, which harbored al Qaeda in the 1990s.

In its latest kind, the deal would see Sudan’s new reformist authorities shell out $335 million to compensate a lot more than 700 victims of al Qaeda’s 1998 terrorist attacks on U.S. embassies in Kenya and Tanzania. In return, Washington would take away Sudan’s designation as a point out sponsor…