HANOI (AFP) - The United States is on track to become the leading foreign direct investor in communist Vietnam, more than 30 years after the end of their war, the head of a US business delegation said Wednesday.

"I'm willing to wager... that within no more than three years - and perhaps a good deal less - the United States will be the largest foreign direct investor in Vietnam," Matthew Daley, president of the US-ASEAN Business Council, told reporters.

"I think the trend line is clear."

He said that in the first quarter of this year, Vietnam registered about six billion US dollars in foreign direct investment, more than half of which, about 3.86 billion US dollars, came from American firms.

The Washington-based US-ASEAN Business Council represents more than 100 US companies. Representatives of 15 of them have joined Daley on a three-day mission that began Wednesday to explore opportunities in Vietnam.

Following the war which ended with Vietnam's reunification in 1975, the US and Vietnam did not normalise diplomatic relations until 1995, followed by trade relations in 2001.

Daley says the United States is either the sixth or 10th ranking foreign investor in Vietnam, depending on which figures are used.

"American interest, as evidenced by investment in Vietnam, has been growing dramatically," he said.