Washington, Jul 18 (IANS): In the midst of a probe demanded by India into the deadly US attack on a motorboat in the Persian Gulf that left an Indian fisherman dead, Washington insisted that the vessel was fired upon after it disregarded nonlethal warnings.

Both Pentagon and the State department Tuesday stuck to a statement issued by the US embassy in Delhi that the USNS Rappahannock had "escalated warning measures" before opening fire at the boat carrying Indian fishermen off the UAE coast in the Persian Gulf.

The incident is under investigation, Pentagon spokesman George Little told reporters Tuesday associating "ourselves with the statement issued by the United States Embassy in Delhi."

"The USNS Rappahannock escalated warning measures in response to a potential threat posed by this vessel," he said. "And this is something that all US Navy ships take into account for security reasons."

"The prospect of potential threats to, especially in the wake of the USS Cole, to put this into some context, there are procedures in place," Little said.

"Based on what we know now, a series of warning measures were issued to the oncoming vessel. Those warnings were not heeded. And the vessel was fired upon," he said.

Asked if the US was planning to apologise for the shooting, Little said, "We certainly regret the loss of life in this incident. (But) There were, in fact, warning measures that were taken based on what we know now."

"This is under investigation. And we'll know the full facts of this incident once that investigation is complete."

State Department spokesman Patrick Ventrell too referred to the statement by US embassy in New Delhi "in which we conveyed our condolences to the families of the crew, which came under fire after the vessel disregarded nonlethal warnings and rapidly approached the US ship."

The US defence department was conducting an investigation, he said. "And we, of course, will work with our Indian counterparts and be as transparent as possible to provide them the results of our investigation once it's finished."