A top White House adviser has attacked the US federal appeals court for upholding a ruling suspending Mr Trump’s travel ban order.
Stephen Miller told US media the court ruling was a “judicial usurpation of power” and that “the president’s powers here are beyond question”.
The court rejected Mr Trump’s attempt to reinstate the ban on Thursday.
His executive order barred citizens from seven mainly Muslim countries from entering the US.
The ban caused chaos at US airports and sparked protests across the country.
Several lawsuits have been filed against the ban, and a federal judge has issued a temporary nationwide block on the travel ban.
Mr Trump has said he may fight the case in the courts, but could also consider issuing a new executive order.
Speaking on Fox News Sunday, Mr Miller accused the 9th US Circuit Court of Appeals, which upheld the block on Mr Trump’s order, of “overreaching”.
He also told ABC’s This Week: “We have equal branches of government in this country. The judiciary is not supreme.”
Under the US system of checks and balances, courts can declare laws, or acts by the president, unconstitutional.