Lawmakers missed a nonbinding deadline to deliver details of a repeal plan Friday, and left a Republican retreat in Philadelphia without reaching consensus on a replacement package that an increasing number of Republicans want to see agreed to before the 2010 law is taken apart.

Complicating the effort, Congress is struggling to find its footing with an unpredictable administration whose actions in only one week have distracted from what lawmakers thought was the top item on the Republican agenda.

Some conservatives worry that delay could be costly, perhaps even fatal, sapping lawmakers’ drive to repeal and sidelining the effort in favor of other priorities, such as keeping the federal government running.