The Pentagon Tuesday played down a confrontation between Chinese vessels and one of its Navy surveillance ships, taking a decidedly more low-key tone than during similar incidents two months ago.

Two defense officials said there have been four incidents in the past month in which Chinese-flagged fishing vessels maneuvered too close to two unarmed ships staffed by civilians and used by the Pentagon to do underwater surveillance and submarine hunting missions. They spoke on condition of anonymity to discuss some of the incidents and details that the Pentagon has not yet released.

The Pentagon did release a brief statement on the latest incident in which two Chinese fishing vessels came to within 30 yards of the USNS Victorius Friday as it was operating in the Yellow Sea.

The Victorious crew sounded its alarm and shot water from its fire hoses to try to deter the vessels in an hour-long incident, one official said. But the vessels didn't leave until the Victorious radioed a nearby Chinese military vessel for help, said Defense Department spokesman Bryan Whitman.

After incidents in March that included similar though less aggressive Chinese maneuvers, the Pentagon protested to Beijing officials and issued a strong public statement calling the Chinese actions harassment.

But on Tuesday, Whitman declined to characterize what the Chinese vessels were trying to do, saying only that their actions were "unsafe and dangerous."

Asked why the tone of the U.S. statement was muted this time, he said: "We will be developing a way forward to deal with this diplomatically."

"USNS Victorious was conducting routine operations on Friday, May 1 in international waters in the Yellow Sea in accordance with customary international law, when two Chinese fishing vessels closed in on and maneuvered in close proximity to the Victorious," the Pentagon said in its statement. "The intentions of the Chinese fishing vessels were not known."

It said the Victorious radioed the WAGOR 17 Chinese government ship, which came and shined a light on one of the fishing vessels. Both of the fishing vessels then moved away.

"WAGOR 17 took positive steps, pursuant to their obligation under Article 94 of the United Nations Convention of the Law of the Sea, to ensure their flagged vessels navigate safely," the statement said.