Rubio reportedly told donors that he will run for the Republican nomination for US president in 2016.
..and the list keeps growing.
Florida senator, Marco Rubio has become the 4th person to declare his 2016 United States presidential bid.
Rubio reportedly told donors that he will run for the Republican nomination for US president in 2016, saying on a conference call that he was "uniquely qualified" to bring the party into the future.
The 43-year old is the 3rd Republican to officially announce a candidacy after Senators Rand Paul and Ted Cruz and is expected to make a formal announcement at a political rally in Miami later on Monday.
Rubio's announcement comes a day after former First Lady and Secretary of State Hillary Clinton said she would stand for the Democratic nomination.
Rubio, who is a Cuban-American, has been a harsh critic of President Barack Obama's policies, especially on immigration and the diplomatic thaw with Cuba.
Referring to Clinton's announcement yesterday in a call with the Associated Press, Rubio said:
"Just yesterday, we heard from a leader from yesterday who wants to take us back to yesterday, but I feel that this country has always been about tomorrow"
BBC reports that the Florida senator, who was first elected in 2010, holds conservative positions on government and military spending, abortion and negotiations with Iran over its nuclear programme.
He is due to speak to supporters at the Freedom Tower in Miami at 18:00 local time.