U.S. naval forces killed "an innocent person" when they fired on an Arab fishing boat suspected of being an Iranian vessel Sunday in the Persian Gulf, a State Department spokesman said yesterday.

While the U.S. government expressed regrets over the incident, the Defense Department insisted that the boat's actions were perceived as hostile and that U.S. forces reacted properly.

The Pentagon reported earlier this week that a U.S. warship fired machine guns at three "suspected" Iranian boats after the vessels approached the American ship at high speed and refused to heed warnings to turn away.

Port officials and witnesses in the United Arab Emirates sheikdom of Sharjah reported that the boats were Arab and that an Indian fisherman was killed by a machine-gun bullet. The witnesses also said the boat in which the Indian was riding was not moving at the time of the attack.

"The United States regrets any loss of life, regardless of the circumstances," State Department spokesman Charles E. Redman said. "We extend our regrets to the Indian government and our condolences to the family of the Indian casualty, Mr. Bikwan Kamgee. We have also expressed our regret to the government of the United Arab Emirates.

The Pentagon, however, defended its actions.

"Our operational procedures are well known," officials said in a prepared statement. "Any action perceived as hostile intent to U.S. ships will be taken seriously."

The Defense Department appeared to back down from statements released Tuesday in which it stood by its initial accounts of an attack on "suspected" Iranian vessels. In yesterday's statement, the Pentagon noted, "The details of the shooting incident are still ambiguous."

One Pentagon official said, "It's warfare on the high seas. What if we hadn't done anything? It goes back to the Stark."

On the USS Stark, 37 sail- ors were killed May 17 when an

Iraqi pilot fired two Exocet mis- siles into the ship. The ship's top commanders resigned from the Navy after investigators found that they failed to defend the ship properly.

Pentagon officials also reported yesterday that one of five dolphins sent to the gulf to help protect U.S. ships from underwater swimmers has died.

One official said the remaining dolphins are losing weight and having problems adapting to the heat and salinity of gulf waters.