The USS Vandegrift's historic visit comes as the two countries have been working to boost bilateral ties, and marks a new attempt at establishing military cooperation.
"I think one of the messages here today is that the ... U.S. and Vietnam are showing the world that former foes can become friends," said U.S. Ambassador Raymond Burghardt.
Burghardt said the U.S. and Vietnamese military have been moving closer together on areas including counterterrorism. However, he said the United States is not looking to re-establish a permanent military presence in Vietnam but wants access to friendly nations' ports instead.
Escorted by a Vietnamese patrol boat, the frigate made its way into Saigon Port with U.S. and Vietnamese flags flying. A chain of white-uniformed sailors stood along the ship's railings as it came in, some holding video cameras and binoculars.
The American group, led by ship Commander Richard Rogers, disembarked down a red-carpeted walkway to be greeted by a Vietnamese delegation headed by Vice Minister for Foreign Affairs Nguyen Duc Hung.
"My first impression is that the river transit today was fantastic," Rogers said. "I think my crew genuinely enjoyed coming up the river and seeing the sights as we came up. My crew is very excited to be here."
The four-day port call follows a landmark meeting last week by Vietnamese Defense Minister Pham Van Tra and U.S. Secretary of Defense Donald H. Rumsfeld — the first time a senior Vietnamese military official has visited Washington.
Bilateral ties have been steadily expanding since diplomatic relations were established in 1995. Trade has risen to more than $3 billion annually with the passage of a landmark agreement in 2001, and Vietnam recently said the United States now ranks as its top importer.
However, the two countries have been less enthusiastic in military-to-military talks. The only issue in that area to see progress was the joint search for Americans listed as missing in action during the war.
The frigate's arrival was symbolic of both nations' efforts to move into a new era of cooperation.
"I think this is a very good sign to promote and develop bilateral relations between Vietnam and the U.S., particularly between the two navies," said Navy Lt. Col. Nguyen Quang Bieu, who was among the welcoming delegation on the dock.
Many Vietnamese say the port call is welcome, demonstrating that old wounds have finally healed in the conflict that killed 58,000 Americans and three million Vietnamese.
"Since Vietnam is now at peace, it's normal for an American Navy ship to be in Vietnam," said Dang Van Hai, 49, a former South Vietnamese soldier who now drives a motorbike taxi.
"I've seen many American veterans who came back. Most of (today's sailors) were not involved in the war and they're visiting many countries and Vietnam is one of their destinations, so I think it's good for them to come back here," he said.
The frigate, part of the U.S. Navy's Seventh Fleet, came from Yokosuka, Japan. The 4,100-ton guided-missile ship carries about 200 crew members.
Visits were scheduled to the Vietnamese Navy Command and Military Zone 7. Also planned was a ceremony in front of City Hall, before a monument honoring Vietnamese Communist leader Ho Chi Minh.
American soldiers once were a constant presence on the streets of Saigon during the height of the war, but U.S. forces pulled out in 1973 after the Paris Peace Agreement was reached. Two years later came the fall of Saigon, the capital of U.S.-backed South Vietnam, to Communist forces. It was renamed Ho Chi Minh City.
On Wednesday, U.S. sailors had permission to go ashore until midnight, after which they were required to either return to the ship, or go to hotels in town.
"I think they will behave themselves," said John Smallman, special agent for US Naval Criminal Investigative Service. At the same time, "we don't want them to be so careful that nobody has any fun."