WASHINGTON – President Barack Obama's sweeping gun-control package faces an uncertain future on Capitol Hill, where majority House Republicans are rejecting his proposals while the president's allies in the Democratic-controlled Senate are stopping well short of pledging immediate action.

The fate of his plan could ultimately hinge on a handful of moderate Democratic senators. Although they are unlikely to endorse the president's call for banning assault weapons, they might go along with other proposals, such as requiring universal background checks on gun purchases.

Several of these senators responded warily after Obama unveiled his proposals Wednesday with the challenge that "Congress must act soon."