Add another to Sen. Rand Paul’s growing list of GOP feuds.

Paul (R-Ky.) took to Twitter on Friday to attack Florida Republican Sen. Marco Rubio on his support for continuing the embargo against Cuba, escalating a public feud that began between the two several days ago.

Rubio hit Paul on Thursday for supporting the White House’s move to open diplomatic relations with the communist country, calling him “clueless” about U.S.-Cuba relations.

“Like many people who have been opining, he has no idea what he’s talking about,” Rubio told Fox News’s Megyn Kelly during a live interview.

Paul then took the fight to Twitter — which he has been known to do from time to time — to push back against Rubio’s comments.

Both Paul and Rubio have indicated their interest in running for president in 2016, although neither candidate has formally entered the race. Paul is reportedly in the early stages of building a campaign infrastructure and is expected to announce whether he will run sometime in the spring.