Holger Richter and Kathrin Kleinbauer, both 31 and travelling by four-wheel-drive, were last heard from on June 19 when they contacted friends by mobile phone while visiting Uluru, or Ayers Rock, in the unforgiving desert interior.
''I want to stress that at this stage we are still treating this as an overdue travelling party,'' Detective Senior Constable Kerry Harris said after a public appeal for information on the missing couple drew no response.
Northern Territory police would decide tomorrow whether to launch a search for the couple, who arrived in Australia last December on a 12-month working holiday, Harris said.
''Inquiries have also commenced with immigration authorities regarding locating their families,'' he said.
Police said Richter and Kleinbauer were well supplied with water and food. They planned to drive on to Darwin before heading to Perth, in neighbouring Western Australia, via the remote 1,400km long Gunbarrel Highway.
Australia's outback can proves deadly for foreign tourists.
British traveller Ethel Hetherington, 52, died near the aboriginal community of Mutijulu, near Uluru, in 2004. British tourist Peter Falconio was murdered on an outback highway in 2001 Australian tourist Oswald Orman, 37, vanished hitch-hiking along the Barkly Highway near Tennant Creek in January, while New Zealander Jamie Herdman was last seen trying to catch a ride at Daly Waters, south of Darwin, last November.
REUTERS RC HT1107