Jimmy Morales, a former TV comic elected Guatemala's new president on a wave of public revulsion against widespread graft, took office Thursday in a ceremony attended by leaders from the Americas.
Invitees to the swearing-in included US Vice President Joe Biden, and the presidents of Mexico, Ecuador and most Central American nations. Spain's former king Juan Carlos also attended.
"Not tolerating corruption or theft, that is something we can do and what we are going to do from the first day," Morales, 46, said as he accepted the presidential sash.
Morales was previously best known for a television role as a country bumpkin who nearly becomes president.
Elections on October 25 elevated him to the office of head of state for real, by a landslide, despite having no political experience beyond an unsuccessful run for municipal office in 2011.
His victory was attributed to widespread public disgust with corruption, especially after his elected predecessor, Otto Perez, was felled by a major graft scandal.
Yet his political support is weak, with his conservative party holding just 11 seats in the 158-seat Congress.
No members from his party sit on the incoming congressional steering committee, and an opposition figure was chosen to be the new speaker in congress.
Morales' party is also fending off charges that some of its founders, former military officers, are linked to atrocities committed during Guatemala's 1960-1996 civil war.
Morales has given few concrete indications of how he intends to make good on his vows to fight corruption, or to combat the country's high murder rate and poverty.
His cabinet was expected to be unveiled hours after the inauguration ceremony, which was delayed more than two hours because of congressional wrangling over its top posts.
Ahead of the swearing-in, Biden met with Morales to congratulate him for vowing to fight corruption in his nation of 16 million people. He also stressed that Guatemala should attract more investment to counter emigration.
Morales asked for Guatemalan migrants in the US to be given "temporary protected status" that would preclude them being deported. Biden said he would analyze the proposal.
Biden and Morales then went into a closed-door meeting with the presidents of Honduras and El Salvador.
Honduran President Juan Orlando Hernandez said after the meeting that the three Central American nations would hold a technical meeting on migration and security in two weeks, then another meeting would be held with Biden in a month's time.
The United States this month launched raids to round up and deport mostly Central American migrants who have court orders to leave the country.
Washington in parallel has allocated $750 million to improve security and prosperity in the so-called Northern Triangle made up of Guatemala, Honduras and El Salvador, which is prey to vicious gang violence.
Guatemala recorded 6,000 murders in 2015, at least half of them blamed on gangs.
Its problems were heightened last year by political instability when protests erupted over a corruption scandal exposing kickbacks to officials in return for lowered customs duties for some companies. That brought about Perez's ouster in September.
Most Guatemalans view Morales with fondness as a familiar figure from his 15-year television career on a program he produced.
His brother Sammy Morales who co-produced the show told a web magazine, Nomada, asserted Jimmy was prepared "academically, emotionally and spiritually" to take on his new role.
According to his official biography, Jimmy Morales, an Evangelical Christian, has a university degree in business administration, a masters in media and communication and another in strategic studies with a specialisation in security and defence.
He has been married for two decades to his wife, Gilda Patricia Marroquin, and has three children.