WASHINGTON (AP) — Three Republican senators on Thursday threatened to hold up health legislation in the Senate unless they got assurances from Speaker Paul Ryan that the House would negotiate a more comprehensive replacement to "Obamacare" and not vote to make the Senate bill law.

Ryan responded that "the House is willing" to convene a conference committee with the Senate to that end. But it was unclear whether the speaker's response would satisfy the senators' demands, leaving health legislation in limbo once again at a crucial moment.

The convoluted developments played out as a divided Senat...