WASHINGTON — Two more Republican senators declared on Monday night that they would oppose the Senate Republican bill to repeal the Affordable Care Act, killing, for now, a seven-year-old promise to overturn President Barack Obama’s signature domestic achievement.

The announcement by the senators, Mike Lee of Utah and Jerry Moran of Kansas, left their leaders at least two votes short of the number needed to begin debate on their bill to dismantle the health law. Two other Republican senators, Rand Paul of Kentucky and Susan Collins of Maine, had already said they would not support a procedural step to begin debate.

With four solid votes against the bill, Republican leaders now have two options.

They can try to rewrite it in a way that can secure 50 Republican votes, a seeming impossibility at this point, given the complaints by the defecting senators. Or they can work with Democrats on a narrower measure to fix the flaws in the Affordable Care Act that both parties acknowledge.