Aust flags Long Tan pact with Vietnam

Australia has flagged entering into a formal agreement with Vietnam on future Long Tan commemorations, to ensure access for veterans to the battle site.

The idea has been suggested by the Veterans Affairs Minister Dan Tehan - although he's yet to raise it with the Vietnamese government.

"Rather than a review ... we need to look at some sort of memorandum of understanding ... which is very clear about how things should proceed into the future," he told ABC radio.

Australian officials at the Long Tan site on Thursday were ensuring visitors complied with limitations imposed by the Vietnamese government after it dropped an initial blanket ban on the site.

In Canberra, hundreds of veterans and their families gathered for morning services at the Australian War Memorial to honour the 18 diggers killed in one of the bloodiest battles of the Vietnam War.

Prime Minister Malcolm Turnbull, Opposition Leader Bill Shorten and Governor-General Peter Cosgrove were among the dignitaries.

Overnight Mr Turnbull and Foreign Minister Julie Bishop held talks with Hanoi officials after Vietnam cancelled a ceremony at the site of the 1966 battle that would have been attended by about 1000 Australian veterans.

Mr Turnbull spoke to his Vietnamese counterpart by phone and urged him to show empathy for those who had made the journey.

As a concession, a wreath-laying ceremony was to go ahead while small groups of 100 or less would be able to visit the Long Tan battle site.

Mr Tehan, who had labelled the initial ban "not the act of a friend", offered his heartfelt thanks for the change of heart.

"I think that is the act of a friend - I think they have realised they've made a mistake and they've sought to address that."

He acknowledged sensitivities in Vietnam around loud music, flags and displays of medals.

Mr Turnbull said the bravery and determination shown throughout Australia's service in the Vietnam War was etched into the national story.

"We acknowledge today the many servicemen and women who were wounded, often in ways we have been too slow to recognise and help.

"Your sacrifice has continued long after your service."

Sir Peter told a stand-to service in Canberra that Long Tan was both a simple and complex battle.

"The simplicity is that it quickly became a battle for survival," he said.

"It was complex in that the indefatigable efforts of others, particularly the artillery, kept those men from being over run."