WASHINGTON, United States (AFP)— Donald Trump will issue a raft of executive orders aimed at reshaping how the United States deals with citizenship and immigration, he said on Monday minutes after his inauguration.

The 47th president will set to work almost immediately with a series of presidential decrees intended to drastically reduce the number of migrants entering the country.

“First, I will declare a national emergency at our southern border,” Trump said.

“All illegal entry will immediately be halted, and we will begin the process of returning millions and millions of criminal aliens back to the places from which they came.

“I will send troops to the southern border to repel the disastrous invasion of our country,” he said.

Trump, who campaigned on a platform of clamping down on migration and whose policies are popular with people who fret over changing demographics, also intends to put an end to the centuries-old practice of granting citizenship automatically to anyone born in the United States.

“We’re going to end asylum,” White House deputy press secretary Anna Kelly told reporters, and create “an immediate removal process without possibility of asylum. We are then going to end birthright citizenship.”

The notion of birthright citizenship is enshrined in the US Constitution, which grants anyone born on US soil the right to an American passport.

Kelly said the actions Trump takes would “clarify” the 14th Amendment — the clause that addresses birthright citizenship.

“Federal government will not recognise automatic birthright citizenship for children of illegal aliens born in the United States,” she said.

Kelly said the administration would also reinstate the “Remain in Mexico” policy that prevailed under the last Trump administration.

Under that rule, people who apply to enter the United States at the Mexican border were not allowed to enter the country until their application had been decided.

“We’re going to… reinstate Remain in Mexico and build the wall,” she said.

Kelly said Trump would also seek to use the death penalty against non-citizens who commit capital crimes, such as murder.

“This is about national security. This is about public safety, and this is about the victims of some of the most violent, abusive criminals we’ve seen enter our country in our lifetime, and it ends today,” she said.

Many of Trump’s executive actions taken during his first term were rescinded under Joe Biden, including one using so-called Title 42, which was implemented during the COVID-19 pandemic preventing almost all entry to the country on public health grounds.

The changes under Biden led to an influx of people crossing into the United States, and images of thousands of people packing the border area.

Trump and his allies characterised this as Biden’s “open border” policy, and spoke regularly of an “invasion.”

The incoming president frequently invoked dark imagery about how illegal migration was “poisoning the blood” of the nation, words that were seized upon by opponents as reminiscent of Nazi Germany.

While US presidents enjoy a range of powers, they are not unlimited.

Analysts say any effort to alter birthright citizenship will be fraught.

Aaron Reichlin-Melnick, a Senior Fellow American Immigration Council, said the 14th Amendment was “crystal clear” in granting citizenship to anyone born in the United States, with the exception of children of foreign diplomats.

“We have had birthright citizenship for centuries, and a president cannot take it away with an executive order,” he told AFP.

“We expect rapid court challenges.”

Reichlin-Malik said all sides of the immigration debate recognised that the laws needed reform, but presidential orders were unlikely to achieve lasting change.

“Instituting new travel bans will make the US legal immigration system even more complex and expensive and difficult to navigate than ever,” he said.

“Our immigration system is badly out of date, and executive actions aiming to restrict it even further will harm the United States.”