A classified October 2001 cable released this week concludes the doomed Siev-X vessel had probably sunk in international waters, not Indonesian waters as claimed by high ranking officials and John Howard.

Tony Kevin, a former Australian diplomat and now Siev-X campaigner said yesterday the official cable was issued from the Australian embassy in Jakarta within hours of the boat sinking with 353 lives lost.

It identified the boat's sinking position as 'unknown, but it is judged as no further south than 8 degreees latitude on a direct line from Sunda Strait to Christmas Island'.

Mr Kevin says this means it sank in international waters well within reach of Australian search and rescue capability.