Algerian President Abdelaziz Bouteflika has said he is sure that 15 Europeans taken hostage in the Sahara desert are alive.
The first group of hostages arrived home in May
Speaking to reporters in Austria, Mr Bouteflika said he would do everything possible to secure their peaceful liberation.
There had been no word about the fate of the 10 Germans, four Dutch and one Swiss since another group of 17 adventure tourists from Europe was freed on 13 May when Algerian troops stormed an Islamic extremist hideout.
The tourists were seized while travelling without guides in the scenic south of the country between February and March and are thought to be held near the Tuareg city of Illizi, 1,200 kilometres (750 miles) south of Algiers.
"We're working with the Germans to find a peaceful way to solve this problem... at a political, security and military level," said the Algerian leader in Vienna.
I would stop at nothing in order to save their lives
Abdelaziz Bouteflika, Algerian President
"We would even go so far as giving the terrorists safe conduct if, in return, the hostages were set free. I would stop at nothing in order to save their lives."
The Algerian president also expressed concern that the missing tourists had not taken proper precautions when coming to his country.
"I regret that the people concerned came to Algeria in ways that are not totally orthodox and normally one should go to these places with specialised people," he said.
Since the tourists' disappearance, four motorcycles and a jeep thought to belong to the group have been found in southern Algeria, the country's El Watan newspaper reports.