MARLBORO - (AP) -- President Barack Obama's sweeping gun control package faces an uncertain future on Capitol Hill. Republicans dominating the House are rejecting his proposals while Obama's allies in the Democratic-controlled Senate are stopping well short of pledging immediate action.

The fate of Obama's 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."

Obama's sweeping, $500 million plan marks the most comprehensive effort to tighten gun laws in nearly two decades.