WASHINGTON — Congress took its first steps toward reversing President Obama's health care reforms Thursday, but Republican leaders are coming under pressure from rank-and-file lawmakers to detail exactly how their “repeal and replace” plans will play out before moving any further.

The Senate voted early Thursday morning on a measure that would allow the use of the special budget reconciliation process to pass health care legislation. That would allow Republicans to act without securing cooperation from Democrats, who have vowed to block major changes.