VIENTIANE: Hillary Clinton landed in Laos Wednesday for a brief but historic trip, becoming the first US secretary of state to visit the communist country in 57 years.

The visit will focus on the legacy of the Vietnam War and a controversial dam project.

“It's a pretty big deal for the Laotians, and we will underscore a number of areas that we're working on together,” a senior US official said.

These include left over ordnance from the war which ended in 1975 as well as the continuing effects of the defoliant Agent Orange, used by US forces to try to flush out communist forces.

The US wants to push for more access for excavating the remains of those missing in action, the official said, adding that two planned trips had been cancelled in the last 16 months due to resistance from the Laotian side.

Another of the main thrusts of the trip will be talks on controversial plans by Laos to build a massive dam on the Mekong River, which governments and environmentalists warn could have a devastating effect on millions of people.

Clinton will be only the second secretary of state to visit Laos after John Foster Dulles, who spent a day in the then-monarchy in 1955.

Experts say that all those years ago they had to clear the water buffalo from the Vientiane airport runway so his plane could land.

Clinton was invited to Laos by Foreign Minister Thongloun Sisoulith in 2010 who was the first top Laotian official to visit Washington since the Soviet-backed communist rebels swept to power, ousting the monarchy, in 1975.

During her four-hour whirlwind trip, she will hold talks with Thongloun as well as with Prime Minister Thongsing Thammavong.