Donald Trump said on Monday that his administration would declare a national emergency and use the US military to carry out mass deportations of undocumented immigrants.

In an early morning social media post, Trump responded “TRUE!!!” to a post by Tom Fitton, the president of the conservative group Judicial Watch, who wrote on 8 November that the next administration “will use military assets to reverse the Biden invasion through a mass deportation program”.

Since his decisive victory, Trump has said he intends to make good on his campaign promise to execute mass deportations, beginning on the first day of his presidency. But many aspects of what he has described as the “largest deportation program in American history” remain unclear.

Trump has previously suggested he would rely on wartime powers, military troops and sympathetic state and local leaders. Such a sprawling campaign – and the use of military personnel to carry it out – is almost certain to draw legal challenges and pushback from Democratic leaders, some of whom have already said they would refuse to cooperate with Trump’s deportation agenda.