Republicans in Puerto Rico are voting Sunday in a primary election to help select a candidate to challenge President Barack Obama in November's presidential election.

Residents of the U.S. commonwealth cannot vote in general elections, but will award 20 delegates to the Republican nominating convention.

The frontrunner, former Massachusetts governor Mitt Romney, and former senator Rick Santorum, both made brief campaign appearances on the island this week ahead of voting.

Santorum caused a stir after suggesting Puerto Rico would have to make English its official language before it could become the 51st U.S. state.

Romney say he supports statehood for Puerto Rico without any language stipulations. Both English and Spanish are recognized languages in Puerto Rico. The delegates will be divided if no candidate gets more than 50 percent of the vote.

The Republican campaign focus next shifts to Illinois, which holds it primary Tuesday, and Louisiana, which votes next Saturday.