Image copyright AFP Image caption Mrs Clinton's landmark visit to Laos is part of a trip signalling growing US interest in Asia

Hillary Clinton has become the first US secretary of state to visit Laos in 57 years, on a trip focusing on economic ties and the legacy of the Vietnam War.

Arriving in the capital Vientiane from Vietnam, she met Prime Minister Thongsing Thammavong and Foreign Minister Thongloun Sisoulith.

The US is spending $9m this year on helping clean up unexploded ordnance left over from the Vietnam War in Laos.

Mrs Clinton will then head to Cambodia for an Asean meeting.

The US dropped two million tons of bombs on Laos during the Vietnam War and unexploded bombs are still affecting lives and agriculture in the South East Asian nation.

The last top US diplomat to visit Laos was John Foster Dulles in 1955.

The US and Laos also "agreed to improve and further facilitate the accounting operations for American personnel still missing from the Indochina War era", said a statement released following Mrs Clinton's meeting with Mr Thongsing.

The two sides also discusssed Laos' pending entry into the World Trade Organization (WTO).

Mrs Clinton visited a Buddhist temple and a prosthetic centre funded by the US, the Associated Press reports.

Another key item on her agenda, reports say, is the controversial Mekong River dam, which critics say would have a major impact on the environment and millions of lives.

The $3.8bn (£2.4bn) hydro-electric dam project at Xayaburi has caused tension among Mekong region countries - Laos, Vietnam, Cambodia and Thailand.

In April, a multi-billion dollar contract was signed for a Thai company, CH Karnchang, to build the dam.

The Lao government has pledged not to go ahead with the project until environmental issues have been resolved.

However, activists say work on the project has already begun, with reports and photographs emerging of construction vehicles in the area.

'Pivot toward Asia'

Mrs Clinton's trip is part of a tour of Asia which analysts say signals the United States' growing interest in the region.

"My trip reflects a strategic priority of American foreign policy today," she told reporters in Mongolia earlier this week.

"After 10 years in which we focused a great deal of attention on the conflicts in Afghanistan and Iraq, the United States is making substantially increased investments - diplomatic, economic, strategic and otherwise - in this part of the world. It's what we call our pivot toward Asia."

At the Asean regional forum later this week in the Cambodian capital, where she will join counterparts from the 10-nation bloc and other Asian countries, including China, tension in the South China Sea is expected to top the agenda.

Mrs Clinton had earlier urged progress on a code of conduct for resolving conflict in the disputed waters between China and several South East Asian nations.