President Donald Trump's administration took its most drastic step yet to roll back the Affordable Care Act, cutting off a subsidy to insurers hours after issuing an executive order designed to draw people away from the health law's markets.

The moves — which critics call deliberate attempts to sabotage the law — come just weeks before Americans will be able to start signing up for coverage for 2018. They follow other steps the Trump administration has taken, such as slashing advertising and outreach budgets to bolster enrollment in Obamacare plans, as well as planning outages of the website where people can sign up.

Shares of publicly traded hospital chains dropped in early U.S. trading, as did insurers such as Centene Corp. that are still present on Obamacare markets. The largest insurance companies in the country have mostly or entirely exited the exchanges, and are unlikely to see much impact.