BAGHDAD (AFP) - A buildup in the U.S. naval presence in the Persian Gulf is intended to send the message that "the United States is an enduring presence in this part of the world," U.S. Defense Secretary Robert Gates said Friday.

"We have been here for a long time, we will be here for a long time and everybody needs to remember that, both our friends and those who might consider themselves our adversaries," Gates told reporters at a briefing in Iraq.

He said that the U.S. naval presence in the Persian Gulf has increased in the past weeks, but would not directly comment on a report that the United States is sending a second aircraft carrier to the Persian Gulf.

"My impression is there has been an increase in naval strength in the Persian Gulf in the past several weeks," he said.

"I don't think it's a response to anything anyone else has done," he said in response to a question on whether the buildup was related to the Iranian nuclear dispute.

As Gates spoke to reporters in front of U.S. military headquarters outside Baghdad, the crackle of gunfire could be heard in the distance.

Gates is wrapping up a three-day visit to Iraq to assess the situation as the U.S. considers changes in strategy there.