Federal officials are looking to clear the air in two US Caribbean territories by requiring cruise liners, tankers and other large ships in the region to reduce their emissions or face penalties.

The plan is to take effect in late 2013. It will target ships traveling in waters around Puerto Rico and the US Virgin Islands, which have some of the busiest ports in the Caribbean, Judith Enck, regional administrator for the US Environmental Protection Agency, said Wednesday.

The two islands were initially excluded from a plan adopted earlier this year by a United Nations agency to control emissions from large ships that sail within 200 nautical miles of the US and Canadian coasts, she said.

"There is a real problem with local pollution,'' Enck said.

The Port of San Juan in Puerto Rico sees more than 1 million cruise ship passengers every year, along with nearly 3,800 cargo ships laden with 11 million metric tons of goods. Some 800 cruise ships arrive every year in nearby St. Thomas, which is the largest cruise port in the US Virgin Islands.

Under the plan, ships will have to use cleaner fuel or install special equipment to reduce air pollution. As a result, the EPA estimates sulfur dioxide and fine particles that are linked to asthma and cancer could be cut by roughly 90 percent within a decade.

Many big ships outside the jurisdiction of the US government often run on fuels with high sulfur levels