U.S. State Department spokeswoman Victoria Nuland, during her media briefing Tuesday, was asked about the incident in which a Chinese warship reportedly locked its weapon-targeting radar on a Japanese Maritime Self-Defense Force destroyer in the East China Sea.
"I will say that with regard to the reports of this particular lock-on incident, actions such as this escalate tensions and increase the risk of an incident or a miscalculation, and they could undermine peace, stability and economic growth in this vital region," a State Department transcript showed Nuland as saying. "So we are concerned about it."
Japan's Kyodo News said the incident occurred last week in the waters off the disputed Senkaku Islands in the East China Sea.
The islands also are claimed by China and the territorial dispute between the two countries has escalated since last September when the Japanese government purchased three of the Senkaku islets from their private owner.
Japan Tuesday lodged a protest with China over the latest incident.
The New York Times quoted Japanese Defense Minister Itsunori Onodera as saying a Chinese frigate directed its radar at a Japanese destroyer Jan. 30.
The Japanese Defense Ministry also said a Chinese frigate directed the same kind of radar at a Japanese military helicopter in another incident earlier in January.
The ministry said in both cases the Chinese ships eventually turned off their radar without actually firing a shot.