The Trump administration asked the Supreme Court Sunday to allow the president to fire the head of a US whistleblower protection agency, his first appeal to the top court since returning to office and issuing a flurry of contested executive orders.

President Donald Trump's declarations have targeted public spending and the dismantling of federal agencies in particular, and have triggered multiple legal challenges.

The White House fired Hampton Dellinger, head of the Office of Special Counsel, on February 7 but Dellinger sued the president and a district court ordered he be reinstated.

The US Court of Appeals on Saturday then rejected the Trump administration's request to overrule the decision.

The emergency appeal filed to the Supreme Court on Sunday branded this an "unprecedented assault on the separation of powers that warrants immediate relief." 

The Supreme Court, which currently includes three Trump-nominated justices, is primed to play a significant role in what some experts are suggesting is a looming constitutional crisis as the president tests the limits of his executive power and the judiciary pushes back.

Trump, who began his second term last month, has launched a campaign led by one of his top donors, Elon Musk, to downsize or dismantle swaths of the US government.

Trump's Supreme Court appeal added that "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 whom the President believes should not be entrusted with executive power and to prevent the President from relying on his preferred replacement."

It warned that the New York court's intervention "exemplifies a broader, weeks-long trend," adding that the Supreme Court should "not allow the judiciary to govern by temporary restraining order and supplant the political accountability the Constitution ordains."

Trump's executive orders have faced growing pushback from the courts with around a dozen court orders issued against the administration from some 40 lawsuits.

This includes an attempt to freeze $3 trillion in federal grants and loans, a deferred resignation program for government workers and a plan to transfer transgender women inmates to men's prisons.

He has also clashed with judges over his attempts to abolish birthright citizenship, sending Venezuelan migrants to Guantanamo Bay, funding cuts to the National Institutes of Health, and placing workers from the US Agency for International Development (USAID) on leave.

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