Flipping the script on a Republican rival, Kentucky Sen. Rand Paul on Friday criticized Florida Sen. Marco Rubio as "an isolationist" as the GOP's intra-party feud over President Obama's new Cuba policy intensified.

The charge was unusual for the libertarian-minded Paul, often cast as an isolationist himself. On Friday, however, Paul made the case for opening up trade and engagement with communist Cuba.

In a tweet, Paul said Rubio, the son of Cuban immigrants, "is acting like an isolationist who wants to retreat to our borders and perhaps build a moat. I reject this isolationism."

Paul was responding to Rubio's comments in an interview the night before with Fox News, in which Rubio said Paul had "no idea what he's talking about" when it comes to Cuba. A Rubio spokesman declined to comment.

The two White House prospects represent opposing viewpoints on Obama's new Cuba policy, which aims to restore diplomatic relations with the communist island, ease economic and travel restrictions and seek to partner with Congress to end the decades-long trade embargo.

Paul was one of the few high-profile Republicans to support Obama's plan to open trade with Cuba. Rubio, who often sides with the GOP's foreign policy hawks, has been critical of Obama's push to establish ties with Cuba, saying it amounts to appeasing the Castro regime.

The exchange offered a preview of a foreign policy debate that could emerge in the next presidential campaign. Rubio and Paul are both considering GOP bids and the Kentucky senator has been pushing back against concerns among establishment Republicans that his libertarian leanings would lead the U.S. to retreat from the rest of the world. Rubio has advocated for a muscular U.S. foreign policy that demands American leadership around the globe.

Despite the clash with Paul, the Florida senator has become the face of Republican opposition to Obama's plan. Senate Republican leader Mitch McConnell, a Paul ally, described Rubio this week as the lawmaker who "knows more about this than almost anybody in the Senate -- if not everybody in the Senate."

Rubio has vowed to prevent Obama from opening an embassy on the island nation with its own ambassador, drawing a sharp response from White House spokesman Josh Earnest. He said it would be "odd" for Rubio to threaten to oppose a U.S. ambassador to Cuba given that he voted for sending Ambassador Max Baucus to China, another country where the U.S. has concerns about the political system and human rights.

Paul largely agreed with the White House in an op-ed published by Time magazine on Friday in which Paul said supporters of the Cuba embargo "fall strangely silent" when asked about trade with Cuba compared with trade with Russia or China or Vietnam.

Paul said he supported engagement, diplomacy and trade with those countries and others "with less than stellar human rights records, because I believe that once enslaved people taste freedom and see the products of capitalism they will become hungry for freedom themselves."