U.S. military challenged maritime claims of 19 countries in 2014

It was the largest number of countries challenged in more than a decade, establishing the program's return to levels from before the wars in Iraq and Afghanistan, when U.S. forces had to curtail operations because of other priorities, officials said.

The rise in operations was due in part to an increased focus on Latin America, where the U.S. military challenged claims of half a dozen countries, including Argentina, Brazil, Venezuela and Nicaragua, according to the Pentagon's annual Freedom of Navigation Report for 2014.

The United States carries out freedom of navigation operations by sending Navy ships and military aircraft into areas that nearby countries have tried to restrict in some way. The operations aim to show that the international community has not accepted claims made by one or more countries.

The operations, which began in 1979, are coordinated by the State and Defense departments and are meant to be consistent with the United Nations Convention on the Law of the Sea, even though Washington has not formally adopted the agreement.

A defense official, speaking on condition of anonymity, said the operations in 2014 occasionally prompted communication between U.S. and agents from the country being challenged, but the encounters were handled professionally and there were no incidents.

A 1988 freedom of navigation operation in the Black Sea resulted in U.S. and Soviet ships bumping. That incident led to a bilateral understanding on the rights warships have in transiting the territorial seas of other states, officials said.

(Reporting by David Alexander; editing by Gunna Dickson)