DONALD Trump's migrant standoff with Colombia was a signal to all world leaders - and shows nothing is off the table, an expert said.
America's allies will have to "roll with the punches" as the president brings his America First agenda back to the world stage.
Colombia caved and accepted the return of its own illegal immigrants after Trump threatened to hit the South American nation with tariffs and sanctions.
Trump had planned to slap a 25 per cent tariff on Colombian imports - and revoke the visas of government officials.
The row came after Colombia stopped two US military aircraft packed with their own citizens from landing in the country last Sunday.
Just two hours after Trump's threat, Bogota did a U-turn and agreed to accept migrants with the White House then dropping the threat.
Read more on Trump
Defiant Don later posted a computer-generated image of him standing beside a sign reading FAFO - which usually stands for "f**k around, find out".
Foreign policy analyst Michael O'Hanlon, from the Brookings Institute, said the migrant standoff was a clear warning to world leaders.
Bogota's backdown will encourage Trump to threaten allies more, he added.
Trump now appears to have a "willingness not to play Mr Nice guy on the world stage" with his second presidency.
Most read in The US Sun
O'Hanlon told The Sun: "I think Trump has realized that - legally and otherwise - the tariff option is a attractive one, and the opening salvos on this front have been encouraging as well."
Don's moves could also make America's allies more friendly to Trump - and change their behaviour as they try and avoid his wrath.
O'Hanlon said: "Trump will certainly feel that the fact that a lot of leaders around the world seem to be trying to engage with him is validation of his basic theory of the case - that he can threaten them.
"I think what they're [allies] getting now is sort of what they knew was coming."
Looking ahead to the next four years, O'Hanlon said the Colombia row hints at what the world can expect from Trump.
O'Hanlon said: "He wants to wield his own personal strength of persuasion, plus the power of the American economy as his main levers for getting his way on a lot of issues."
But O'Hanlon said this kind of blustery approach does carry risks - and potentially spark an unwanted conflict.
Tensions could spiral if Trump removes US troops from South Korea, revoked Nato's Article Five protection from some eastern European countries - or continued to say he wouldn't back Taiwan in a Chinese invasion, O'Hanlon said.
Trump has made it clear he expects US military support to be paid for by allies - not just conditional on alliance agreements.
In those cases, North Korea, Russia, and China could see that as American weakness or an unwillingness to fight and invade.
He said: "The question is going to be in the five or 10 places where there is a big fight, what are the consequences?
"We haven't really seen decisions of major consequence [yet].
"If that happens, then people will have to reassess."
In the case of Taiwan, O'Hanlon said Trump could change his mind and back the country if China invaded - even if he said he wouldn't.
The president could "decide that the very fact of this aggression has now made Taiwan more important than he previously thought".
"Trump might decide China is more of a menace than he even fully appreciated, if something that he's done encourages China to attack," O'Hanlon added.
"Trump doesn't care about America's reputation per se.
"I don't think he cares that much what other people think about him, home or abroad and so the idea of protecting some image of the United States is exactly what he's not about."
Warning for Britain
With Trump putting America first, he may be even happy to risk the special relationship with Britain - no matter the cost.
O'Hanlon said: "It seems that he's more favorably inclined than not, but he's not completely sold that this is an automatically special relationship, no matter what."
Starmer, he added, would need to be like Xi Jinping and project "self-confidence", "directness", and "roll with the punches" in order to build a close alliance with Trump and get favourable deals with the United States.
The Labour PM would need to build an agenda with Trump where the pair can work together.
In his first days in office, Trump has declared illegal immigration a national emergency and imposed a crackdown.
He directed the US military to help with border security, issued a broad ban on asylum, and took steps to restrict citizenship for children born on US soil.
The Colombia standoff is being hailed as a victory for Trump.
After Bogota backed down, the White House said: "Today's events make clear to the world that America is respected again.
"President Trump expects all other nations of the world to fully cooperate in accepting the deportation of their citizens illegally present in the United States."
I don't think he cares that much what other people think about him, home or abroad and so the idea of protecting some image of the United States is exactly what he's not about
Michael O'Hanlon
But Colombian President Gustavo Petro accused Trump of being a "white slaveholder" who is on track to "wipe out the human species" after being humiliated by the US leader.
"You don't like our freedom, okay. I don't shake hands with white slavers," Petro said.
"Overthrow me, President, and the Americas and humanity will respond... you can try to carry out a coup with your economic strength and your arrogance."
Colombia's foreign minister Luis Gilberto Murillo said it had "overcome the impasse" with the US just hours after Petro condemned what he called Trump's "blockade".
Washington's draft measures - now on hold - included imposing 25 per cent tariffs on all Colombian goods coming into the US, which would go up to 50 per cent in one week.
READ MORE SUN STORIES
It also included a travel ban and visa revocations for Colombian government officials, as well as emergency treasury, banking, and financial sanctions.
Trump also threatened enhanced border inspections of Colombian nationals and cargo.
Trump's Done List
DONALD Trump has taken office and hit the ground running as he looks to make his second administration a blazing success.
Already, he has renamed the Gulf of Mexico to the Gulf of America and renamed Mount McKinley back from is indigenous name Denali.
Trump declared an official national emergency at the US-Mexico border after he took office.
He can now use federal funding to build a wall along the boundary without the permission of Congress.
He also signed a directive to end birthright citizenship - when a person born on US soil is given American citizenship.
Protected by the Constitution - this order is likely to come up against hefty legal challenges during his term.
Trump also signed an order to designate Mexican drug cartels and certain gangs from El Salvador or Venezuela as foreign terrorist organisations.
This could give his government more powers to go after the criminal organisations with military strikes or to forcefully remove their members from the US.
Trump also withdrew from the Paris Climate Agreement - just as he did at the beginning of his first term.
Trump has also declassified secret documents with information on the assassinations of JFK, RFK, and Martin Luther King Jr.