WASHINGTON - The U.S. military carried out freedom of navigation operations challenging the maritime claims of China, Iran and 10 other nations last year, asserting its right to use the seas in defiance of their restrictions, a Pentagon report said Thursday.

The Defense Department's annual Freedom of Navigation Report to Congress for the 2013 fiscal year showed the U.S. military targeted not only countries such as Iran, with whom it has no formal relations, but treaty allies like the Philippines, too.

The U.S. military conducted multiple operations targeting China over what Washington believes are "excessive" claims about its maritime boundaries and its effort to force foreign warships to obtain permission before peacefully transiting its territorial seas.

U.S. operations challenged Iran for trying to restrict the use of the Strait of Hormuz to ships from countries that have signed the U.N. Convention on the Law of the Sea, an accord the United States has not formally adopted but treats as generally accepted customary law.

The report covers activity in the 2013 fiscal year that ended Sept. 30, before the latest tensions over an incident between U.S. and Chinese warships in the South China Sea and Beijing's declaration of an air defense identification zone over the East China Sea, which Washington rejected.

The United States carries out freedom of navigation operations by sending Navy ships into disputed areas in an effort 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 U.N. Law of the Sea Convention, even though Washington has not formally adopted the agreement.

A U.S. defense official, speaking on condition of anonymity, said the country whose laws are being challenged often are not even aware a U.S. ship has been there, which is one reason for issuing an annual report after the fact to note the complaint.

"There are times that coastal states detect us executing the operation and we respond (with a) bridge-to-bridge query and they tend to be professional," the official said.

Incidents like the 1988 bumping of two U.S. ships by Soviet vessels during a freedom of navigation operation in the Black Sea are uncommon, he said. That incident led the two countries to reach a bilateral understanding on the rights warships have in transiting the territorial seas of other states.

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US freedom of navigation operations targeted China