HANOI, Dec 19 (Reuters) - Vietnam wants to expand its

international defence cooperation to build trust and prevent

wars, its prime minister said on Thursday, and the United States

said it was hopeful its defence industry could play a key role.

In remarks to open Vietnam's second international arms fair,

Prime Minister Pham Minh Chinh said the expo was "a message of

peace, cooperation and development".

The arms fair, which will run until Sunday, is being held at

Gia Lam Airport in Hanoi, with nearly 250 exhibitors from dozens

of countries, including the United States, China, Russia,

Britain, Iran and Israel.

Chinh said Vietnam would maintain its "four no" policy of

not participating in military alliances, not aligning with one

country to oppose another, not allowing foreign military bases

or the use of its territory against another country, and not

using force or the threat of it in international relations.

On the sidelines of the expo, U.S. Ambassador to Vietnam

Marc Knapper said U.S. defence firms could team up with

Vietnamese counterparts in multiple areas, including joint

production and technology transfers.

"We seek to have our great defence companies working here

with Vietnam on things potentially like joint production and

technological transfers," he told a press conference, together

with senior U.S. defence and military officials.

"Our goal is to ensure that Vietnam has what it needs to

defend its interests at sea, in the air, on the ground and in

cyberspace," he said.

Vietnam is a major importer of weapons, especially from

Russia, having invested for years in its defence capabilities in

an unstable region where it has clashed with China over

boundaries in the South China Sea.

The U.S. briefing was conducted next to a Lockheed Martin

C-130 displayed at the expo. Boeing ( BA ) and Textron

Aviation Defense are also present at the Hanoi expo.

Sources have told Reuters that Lockheed Martin ( LMT ) is in talks

with Vietnam for a possible deal on the military transport

plane.

At the briefing, Jedidiah Royal, Principal Deputy Assistant

Secretary of Defense for Indo-Pacific Security Affairs, also

said the U.S. policy for the region would not change when a new

administration takes over in Washington next year.