WASHINGTON (AP) — The Latest on President Donald Trump and health care (all times local):

Donald Trump. REUTERS/Mike Segar President Donald Trump is inviting congressional Democrats to "call me to fix" America's healthcare system, as he prepares an order ceasing federal subsidy payments to health insurers.

In a predawn post on his Twitter account Friday, the president reiterated his oft-stated argument that "Obamacare is imploding."

Addressing Democrats, he tweeted that "massive subsidy payments to their pet insurance companies has stopped," adding: "Dems should call me to fix!"

Since his presidential campaign and nearly nine months in office, Trump has persistently called for getting rid of the Affordable Care Act, the 2010 Obama-era healthcare law. His fellow Republicans joined him in that cause, but neither Trump nor the GOP has been able to muster sufficient strength to get a repeal bill through the Senate.

In a brash move likely to roil insurance markets, Trump says he will "immediately" halt payments to insurers under the ACA, which he has been trying to unravel for months.

The Department of Health and Human Services made the announcement in a statement late Thursday. "We will discontinue these payments immediately," said the acting health and human services secretary, Eric Hargan, and the Medicare administrator, Seema Verma. Sign-up season for subsidized private insurance starts November 1, in less than three weeks, with about 9 million people currently covered.

In a separate statement, the White House said the government could not legally continue to pay the so-called cost-sharing reduction subsidies because they lack a formal authorization by Congress.