Germany, five of whose citizens are among the captives, has been negotiating with the kidnappers since the group was snatched on Friday while on a Sahara desert safari to a remote plateau in the southwestern corner of Egypt, according to Egyptian officials.
Negotiations have been taking place through two phone calls a day between the tour company's Egyptian owner, who was among those kidnapped, and his German wife, who lives in Egypt, an Egyptian security official said, speaking on condition of anonymity because he was not authorized to discuss details of the talks.
Germany has been silent on any negotiations, refusing to even confirm that it is conducting them.
The kidnappers' identity remains a mystery. They are believed to be desert tribesmen, and Egypt's state news agency MENA has said they are demanding up to $15 million in ransom.
Sudan said Tuesday it believes they are Egyptians, but MENA on Wednesday quoted an unidentified Egyptian security official denying they were Egyptians. In one of his initial calls to his wife, the tour operator reportedly described the kidnappers as "African" in appearance.
The five Germans, five Italians, a Romanian, and eight Egyptian guides and drivers were abducted while visiting the Gilf al-Kebir, an isolated plateau some 550 miles southwest of Cairo in Egypt's Western Desert. Only a few hundred adventure tourists a year make the grueling desert journey to the Gilf, drawn by its dramatic desert scenery and rich troves of prehistoric cave art.
Sudan says the kidnappers and their captives have been located in the desert of northwestern Sudan, about 15 miles from the Egyptian border.
"We are now in remote surveillance (of the kidnappers) but we are not planning to storm the place or threaten the lives of hostages," Sudanese Foreign Ministry spokesman Ali Youssef told The Associated Press. "No military action is considered at all."
It was the first such abduction of tourists in Egypt, a country that was plagued in the 1990s by Islamic militant bombings and shooting against tourists. The militant violence was largely suppressed a decade ago.
Egyptian officials have underlined that the kidnapping was not connected to terrorism, but was by "criminals" seeking ransom.
The isolated region around the Gilf is a crossroads for nomadic tribes in Libya, Sudan and even Chad, and lies on routes used by drug smugglers. It has seen a few previous robberies of tourists, according to tour operators.