On his first day on the job, new US Secretary of State Marco Rubio said on Tuesday that his mission "will not be easy."

Marco Rubio said, during a speech he gave to his ministry employees: "The world has changed a lot in the past period, and we must know what will happen in the future."

He added: "My mission will not be easy. There will be challenges and difficult times, and we will seek to avoid conflicts, but not at the expense of our values."

He continued: "Our foreign policy is based on our interests first... and if our interests intersect with the interests of others, we will work with them."

The new US Secretary of State stressed: "Our mission is to promote peace around the world and we will be defenders of our values."

The US Senate unanimously confirmed Marco Rubio as Secretary of State on Monday evening, making him the first member of President Donald Trump's cabinet.

Rubio, the Republican senator from Florida, is among Trump's least controversial candidates, and the vote in his favor was decisive, 99 to none.

Rubio, a member of the Senate since 2011, is described as a "traditional hawk on foreign policy," according to the American newspaper, The Washington Post.