Colombian President Abelardo de la Espriella vowed to restore order and eradicate "narco-terrorists" in a fiery first speech as leader on Friday.
The US-backed millionaire flew by helicopter to address soldiers in a military garrison after his inauguration in the southwestern city of Cali.
His mandate marks a sharp turn right for the Andean nation, with the 48-year-old keen to cozy up to Washington and come down hard on Colombia's patchwork of armed groups.
"There will be no room for maneuvers that undermine the stability of the nation," the president, who adopted a stiff military salute on the campaign trail, told hundreds of soldiers.
He pledged to "relentlessly defeat narco-terrorism," adding that "the option of dialogue is completely exhausted" -- a reference to the former administration's spluttering peace talks with guerrillas.
The first thing on his to-do list, he said, was to join US President Donald Trump's regional anti-cartel alliance known as Shield of the Americas.
The US leader now has an eager ally in Bogota, and the feeling appeared to be mutual late Friday, when the US State Department issued a release saying the Trump administration intends to work with Congress to announce "$1 billion in assistance as part of a security package to support" the new administration.
De la Espriella, who holds dual US and Colombian citizenship, has offered to host US troops on Colombian soil and wants to bomb jungle cocaine labs, build "mega-prisons" and slash the size of the state.
- Unusual inauguration -
In a break with tradition, his inauguration took place in Cali, Colombia's salsa capital, not at Congress in more buttoned-down Bogota.
Among the guests was beleaguered FIFA boss Gianni Infantino, who faces scathing criticism over his now-shelved plan to open the World Cup and other competitions up to private investment.
Right-wing figures also attended, including Argentina's President Javier Milei and Todd Blanche, Trump's acting attorney general, who headed the US delegation.
De la Espriella's leftist predecessor Gustavo Petro declined to attend the ceremony.
He earlier left the presidential residence in the capital, bidding "farewell, freedom and life."
- 'A lot to prove' -
Cali has suffered several guerrilla attacks in recent years, and the city saw beefed-up security for the occasion including 11,000 troops and an anti-drone system.
De la Espriella's narrow victory of less than one percentage point ended four years of Colombia's first-ever leftist government.
He is now faced with a divided Congress, where he lacks a majority.
Supporters are hoping for a harsh crackdown on crime and dissident armed groups.
"This government has a lot to prove. A lot was said during the campaign," 46-year-old Marisol Peira told AFP in Cali.
Petro tried and failed to negotiate peace with the country's myriad armed groups.
Experts say the gangs -- once ideological but now focused on making money from cocaine trafficking and other illicit trades -- used government truces as cover to grow.
Petro, who has claimed election fraud without providing evidence, called for mass protests in major cities on Friday, and hundreds of people peacefully demonstrated in Bogota and Barranquilla.
- Plan Colombia -
De la Espriella's victory is yet another notch in the belt for Latin American right-wingers after electoral wins from Chile to Costa Rica on the back of security promises.
The former lawyer wants to eliminate coca crops used for cocaine production "by all means," advocates the environmentally harmful practice of fracking, and plans to lower taxes for the rich.
Calling himself "The Tiger," De la Espriella plans to forge a military alliance with the United States and Israel to aid his war on guerrillas.
His so-called "Plan Colombia II" is a nod to a multimillion-dollar agreement with Washington in the 2000s aimed at combating drug cartels and leftist groups.
"We have to support him so there won't be so much crime," said German Angulo, a 63-year-old contractor. "We need a complete change."
Although the original "Plan Colombia" succeeded in weakening key combat groups, it also led to allegations of serious human rights abuses.
