By Brad Ryan

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The effects of the US government shutdown are being felt across America as the White House warns federal workers will be fired en masse if Democrats don’t back down.

The Trump administration has also frozen billions in funds for major New York City projects, widely seen as a tactic to put pressure on New York senator Chuck Schumer, who is leading the Democrats’ effort in the shutdown fight.

The shutdown, which only applies to government services deemed non-essential, took effect at midnight, local time, after senators failed to pass a spending bill to keep funding government agencies.

Democrats demanded the bill include healthcare provisions that Republicans refused to pass. They include reversals to Republican cuts, and extensions to existing tax credits for health insurance.

Republicans said the provisions would reopen the door to funding care for unauthorised migrants.

Hundreds of thousands of US government workers will not be paid until the shutdown is over.

Some have been told to stay home; others are required to work without knowing when they will be paid.

Many of the most visible early impacts of the shutdown hit tourist sites.

National attractions like the Library of Congress, US Botanic Garden and Liberty Bell have closed, and Washington’s Smithsonian museums are set to shut next week.

National parks are “generally” being kept open, but almost 10,000 park workers are furloughed so many visitor services have stopped.

Other government activities that have been suspended include:

accepting new patients at the NIH Clinical Centre, America’s largest health research hospitalinspecting food and pharmaceutical production facilitiesprogressing or issuing new defence contractspublic health communications from the Centers for Disease Controlresearch and analysis of economic data

So far, services such as healthcare, law enforcement, border control, public education and postal deliveries are relatively unaffected.

Members of the military will remain at their posts, and National Guard troops deployed to several cities for a “crime crackdown” have also been told to keep working.

Unusually, Vice-President JD Vance joined Ms Leavitt for her regular White House press briefing to bolster Republican messaging in the political blame game.

He said no decisions had made about which federal employees would be fired, and attacked Democrats for taking critical services “hostage” over policy disagreements.

“I actually don’t think it’s going to be that long of a shutdown,” he said.

“This is a pure guess from the vice-president of the United States, because I think you already saw some evidence that moderate Democrats are cracking a little.”

Democratic members of Congress say they are staying in Washington during the shutdown to negotiate with Republicans, who they accuse of disappearing on “vacations scattered across the country”.

“What we’re fighting for is to protect the health care of the American people, which has been under relentless assault,” Hakeem Jeffries, House minority leader and leader of the House Democratic Caucus, said.

“They [Republicans] are asking Democrats to participate in doing more damage to the quality of life of everyday Americans. And we’re not interested.”

The Trump administration’s budget director, Russ Vought, said about $US18 billion ($27 billion) would be withheld from New York infrastructure projects, including a new rail tunnel under the Hudson River.

He said the shutdown had caused a review of the projects’ contracting processes to be put on hold, and the payments would therefore not be processed.