A split among Senate Democrats threatens to derail a U.S.-brokered deal to help Sudan establish a stable civilian government and resolve terror victims’ claims against the former regime of Omar al-Bashir, which harbored al Qaeda in the 1990s.

In its latest form, the deal would see Sudan’s new reformist government pay $335 million to compensate more than 700 victims of al Qaeda’s 1998 terrorist attacks on U.S. embassies in Kenya and Tanzania. In return, Washington would remove Sudan’s designation as a state sponsor of terrorism and restore its sovereign immunity from additional liability in U.S. courts.

At least two senior Democratic senators, however, say the deal is inadequate, according to congressional aides, and want to see greater payouts for foreign victims of the terrorist attacks. They also want to make Sudan compensate an additional group of victims—those of al Qaeda’s Sept. 11, 2001 attacks, for which Sudan denies complicity.

The U.S.-brokered plan is aimed at opening the impoverished nation to commercial investment and more aid from international organizations, while protecting its assets from plaintiffs in terrorism-related lawsuits. Advocates say such measures would shore up the fragile transitional government, which has pledged to establish democratic institutions and repealed harsh religious laws, including those limiting women’s rights and prescribing death for apostasy.