A $625 billion defense bill that establishes military policy stalled in the Senate on Wednesday as Democrats and Republicans struggled over how to move ahead on the massive measure.

Republicans insist on an open process that would allow them to vote on amendments to the popular defense authorization bill that has become law every year for the past half century. Senate Majority Leader Harry Reid, D-Nev., is trying to limit amendments and wrap up the legislation in a few days, avoiding a vote on a possible measure to impose new penalties on Iran and another on health care.