The U.S. Navy is unlikely to carry out another patrol within 12 nautical miles of Chinese-built islands in the South China Sea this year as officials had initially suggested, three U.S. defense officials said on Monday.

Naval commanders had hoped to carry out another "freedom of navigation" exercise in the region as early as December as part of a plan to regularly send vessels into the area and exercise what the United States views as its rights under international law, officials have said.

But the Obama administration, which is weighing the risks of raising tensions with Beijing at a time when the United States is focused on the fight against Islamic State, has not approved the next such patrol, said the officials, who asked not to be named.