MANILA — The Philippines’ top defense official said on Tuesday that the government should review a decades-old treaty with the United States, its longtime ally, to avoid provoking a potential armed conflict with China in the disputed South China Sea.

The security environment in the region has become “much more complex” since the countries’ Mutual Defense Treaty was drawn up 68 years ago, said the Philippine defense secretary, Delfin Lorenzana.

“The Philippines is not in a conflict with anyone and will not be at war with anyone in the future,” Mr. Lorenzana said.

Since President Trump took office, the United States has been conducting more frequent military patrols in disputed waters of the South China Sea, in an effort to counter China’s conversion of contested islands into military bases.