Sen. Rand Paul of Kentucky trolled Sen. Marco Rubio of Florida, his potential rival for the 2016 Republican presidential nomination, on Twitter Friday over Rubio’s opposition to President Obama’s plan to normalize relations with Cuba.  

Hey @marcorubio if the embargo doesn’t hurt Cuba, why do you want to keep it?

— Senator Rand Paul (@SenRandPaul) December 19, 2014

Paul’s twitter-storm comes after the president announced sweeping changes in relations with Cuba Wednesday, including expanding exports, relaxing travel restrictions and renewing diplomatic relations with ambassadors and embassies.

Paul’s position puts him at odds with most Republicans, including incoming Senate Majority Leader Mitch McConnell, R-Ky., who in a recent interview said he defers to Rubio, a Cuban-American, on the issue, and Speaker John A. Boehner, R-Ohio, who torched the move.

The Kentucky Republican, who often gets tagged with the isolationist label by his critics, said Rubio is “acting like an isolationist who wants to retreat to our borders and perhaps build a moat. I reject this isolationism.”

Paul drew an analogy with China and Vietnam, which are both communist nations with which the U.S. now has normalized relations. “So why not Cuba?” Paul asked.