The Trump administration will immediately stop making critically important payments to insurers who sell Obamacare health plans, a bombshell move that is expected to spike premium prices and potentially lead many insurers to exit the marketplace.

The decision to end the billions of dollars worth of so-called cost-sharing reduction (CSR) payments came after months of threats by President Donald Trump to do just that. The news came only hours after Trump signed an executive order that Obamacare advocates said could badly harm the individual insurance marketplaces.

Advocates, along with insurers, health-care provider groups, patient groups and officials in many states, have expressed concerns for months that the cost-sharing reimbursements would be cut off by Trump.

Senate Minority Leader Chuck Schumer, D-N.Y., sharply criticized Trump in a series of Twitter posts late Thursday.

Chuck Schumer tweet: Sadly, instead of working to lower health costs for Americans, it seems @POTUS will singlehandedly hike Americans' health premiums.

Chuck Schumer tweet: @POTUS Make no mistake about it, @POTUS will try to blame the Affordable Care Act, but this will fall on his back and he will pay the price for it.

Two months ago, the Congressional Budget Office estimated that individual health plan premiums would be 20 percent higher than originally projected if the payments ceased. It also projected that premiums would be 25 percent higher than they otherwise would be by 2020, and that the federal deficit would be increased by almost $200 billion if the subsidies ended.

The payments, worth $7 billion or so to insurers this year and up to $10 billion or more next year, reimburse insurers for discounts in out-of-pocket health costs they give to low-income Obamacare customers. The discounts must be offered by law.