President Donald Trump's attempts to shrink the federal bureaucracy are heading to the Supreme Court, according to US media.

He has filed an emergency appeal to the country's highest court to rule on whether he can fire the leader of an independent whistleblowing agency.

Hampton Dellinger, head of the US Office of Special Counsel, sued the Trump administration after he was fired by email this month.

Trump has also sacked more than a dozen inspectors general at various federal agencies along with the jobs of thousands of employees across the US government.

Mr Dellinger, who was nominated by Joe Biden, the former president, argues that his removal broke a law that protects leaders of independent agencies from being fired by the president, "except in cases of neglect of duty, malfeasance or inefficiency".

A federal judge in Washington DC issued a temporary order on Wednesday allowing Mr Dellinger to hold on to his position while the case is being considered.

On Saturday, a divided US Court of Appeals in the nation's capital rejected the Trump administration's request to overrule the lower court.

That has led to the justice department filing an emergency appeal to the conservative-dominated Supreme Court. It is the first case the president has taken to the justices since he took office last month.

"This court should not allow lower courts to seize executive power by dictating to the president how long he must continue employing an agency head against his will," Sarah M Harris, acting solicitor general, wrote in the filing provided by the Department of Justice to the Washington Post.

"Until now, as far as we are aware, no court in American history has wielded an injunction to force the president to retain an agency head," the acting solicitor general wrote, according to the Associated Press news agency.

The Republican president's orders on immigration, transgender issues and government spending have also become bogged down in dozens of lawsuits in the lower courts. Those cases may ultimately wind up at the Supreme Court, too.

Trump's efforts to reduce and reshape the 2.3 million-strong civilian federal workforce continued over the weekend.

Workers in various health agencies who are still within their probation periods received letters on Saturday evening informing them they would be terminated, sources told CBS News, the BBC's US partner.

"Unfortunately, the agency finds that you are not fit for continued employment because your ability, knowledge and skills do not fit the agency's current needs, and your performance has not been adequate to justify further employment at the agency," read the letters.

At least 9,500 workers at the Departments of Health and Human Services, Energy, Veterans Affairs, Interior and Agriculture have been fired by Trump, according to a tally from Reuters news agency.

Another 75,000 workers have taken a buyout offered to get them to leave voluntarily, according to the White House.

The cost-cutting initiative has been led by the Department of Government Efficiency, or Doge, a task force led by Elon Musk.