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• 5 choices on ballot
• Statehood opponents fear assimilation
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SAN JUAN, Puerto Rico (CNN) -- A majority of Puerto Rican voters have rejected the idea of becoming the 51st U.S. state in favor of maintaining the island's current commonwealth status, according to preliminary results from a Sunday plebiscite.

With about two-thirds of the votes counted, statehood had garnered about 46.7 percent of the votes, while 50.2 percent had voted "none of the above," a choice being pushed by commonwealth supporters. The remaining 3 percent was split among three other options listed on the ballot.

About 70 percent of the Caribbean island's 2.2 million registered voters participated, according to election officials.

If those results hold up, Sunday's vote will mark the third time since 1967 that Puerto Ricans have rejected statehood. That would be a blow to Gov. Pedro Rossello, who called the nonbinding plebiscite in hopes that a strong pro-statehood result would persuade the U.S. Congress to approve the idea.

But Puerto Rican Senate President Charlie Rodriguez said statehood supporters intended to press ahead with their campaign, despite the results.

"Puerto Rico is on an irreversible path toward statehood," he said.

5 choices on ballot

Voters were given five choices Sunday, which included becoming a state, remaining a U.S. commonwealth, declaring independence or entering into a "free association" with the United States that would be somewhere between commonwealth and independence. The fifth choice was none of the above.

Supporters of retaining the current commonwealth status --primarily the opposition Popular Democratic Party -- pushed for a none-of-the-above vote because they objected to the way the commonwealth option was described on the ballot.

"We are very happy with our commonwealth, and we want to keep it," said San Juan Mayor Sila Calderon, a Popular Democrat, as she voted. "Today, we Puerto Rican people are asserting our identity, our love for commonwealth, our love of our U.S. citizenship."

Puerto Rico, which has 3.8 million residents, became a U.S. territory in 1898 as a result of the Spanish-American War. It became a commonwealth in 1952.

Under commonwealth status, Puerto Ricans are U.S. citizens subject to many federal laws and the military draft. While they receive some federal benefits, they don't pay U.S. taxes unless they move to the mainland.

Puerto Rico does not get voting representation in Congress, and residents don't get to participate in U.S. presidential elections unless they become residents of other states.

Statehood opponents fear assimilation

Supporters of statehood say it would bolster Puerto Rico's economic development and give its people full democratic rights enjoyed by other U.S. citizens. But opponents fear that the mostly Spanish-speaking island's language and unique culture will be lost if incorporated into the English-oriented mainland.

Under the current arrangement, the net amount of federal money transferred to Puerto Rico each year is about $10 billion. Some in Congress, who believe that level of financial transfer should not continue, have warned that commonwealth status must eventually give way to either statehood or independence.

However, the idea of making Puerto Rico a state has its critics on the mainland, who say the island is too poor, too remote and too unlike the other 50 states.

In a pre-election commentary in the San Juan Star, Gerda Bikales of the group English Language Advocates said making Puerto Rico a state would be "a nightmare of our own making."

"I can assure the people of the island that mainstream America will not accept into its fold a new political entity with all the characteristics of a foreign nation," she said.

Reuters contributed to this report.