The House Freedom Caucus says it has enough votes to block the Obamacare repeal measure.
The president’s warning came a day after GOP leaders made several changes to their measure.
It would do away with the Affordable Care Act’s requirement that all Americans have health coverage or pay a fin.
Lawmakers might limit what employers exclude from workers’ taxes for health insurance benefits.
A House bill would allow new employees at start-ups to defer paying taxes on stock options.