Marco Rubio has been sworn in as US Secretary of State after being confirmed by the Senate in a unanimous vote.
The US Senate unanimously approved Mr Rubio for the role, putting him on the front line of President Donald Trump's often confrontational diplomacy.
Mr Rubio, who is the first Hispanic and first fluent Spanish speaker to assume the position of top US diplomat, is Mr Trump's first cabinet nominee to be confirmed by the Republican-led Senate, only hours after the inauguration.
Unusually in a highly partisan era, Mr Rubio was confirmed 99-0, with several Democratic senators describing him as a friend.
One Senate seat was made vacant by the inauguration of Vice President JD Vance.
"Given the uncertainty around the globe right now, it is in America's interest not to skip a beat and to fill this role immediately," said Senator Jeanne Shaheen, the top Democrat on the Senate Foreign Relations Committee.
"While we may not always agree, I believe he has the skills, knowledge and qualifications to be secretary of state," she said on the Senate floor.
Ms Shaheen and the Republican chairman of the committee, Jim Risch, agreed to fast-track Mr Rubio's nomination, which was cleared by the panel barely an hour before heading to the floor.
"It's no secret that hostile powers from China to Russia, from North Korea to Iran, have formed an authoritarian axis bent on weakening the United States," Mr Risch said.
"We need a principled, action-oriented chief diplomat like Marco Rubio to take them on."
Mr Rubio will immediately have the task of executing the potentially erratic foreign policy of Mr Trump, who in his inauguration speech renewed threats to seize the Panama Canal but also pledged to be a "peacemaker."
Demonstrators were seen burning US flags during a protest outside the residence of the US ambassador in Panama City during a rally against the inauguration of Donald Trump.
Mr Trump challenged the two secretaries of state in his first term with a foreign policy that swung rapidly, with Mr Trump in one case shifting from threatening destruction of North Korea to declaring that he "fell in love" with leader Kim Jong-un.
Mr Rubio, the working-class son of Cuban immigrants who bitterly opposed Fidel Castro's communist revolution, is known for his hawkish stance toward Latin American authoritarian states and China.
In his confirmation hearing last week, he accused China of cheating its way to superpower status and called it "the most potent and dangerous near-peer adversary this nation has ever faced."
Mr Rubio will head to work today and, according to diplomats, is expected to meet with foreign ministers from the Quad, which groups the United States with Australia, India and Japan.
Conceived by late Japanese prime minister Shinzo Abe and upgraded by former president Joe Biden, the Quad has been seen by China as a way for the four democracies to encircle and contain it, despite denials from the countries.
Mr Rubio is also expected to join Mr Trump in being a stalwart defender of Israel, which on Sunday earlier entered a long-awaited ceasefire with Hamas, something that had been sought exhaustively by Mr Rubio's Democratic predecessor Antony Blinken.
Despite his collegial relations in the Senate, Mr Rubio was once a bitter opponent of Mr Trump, who famously belittled him as "Little Marco" when the senator unsuccessfully sought the Republican presidential nomination in 2016.
Mr Rubio has since rallied behind Trump. In his confirmation hearing, he repeatedly stressed that the president would make the policy.
Several of Mr Trump's nominees have yet to have confirmation hearings due to their controversial records, including Tulsi Gabbard for intelligence chief, Robert F Kennedy Jr for health and human services secretary and Kash Patel for the FBI.
Senate Democratic leader Chuck Schumer said that Mr Rubio's confirmation showed the party would not "reflexively oppose nominees" but would also not "rubber stamp" them.
