Al Jazeera's Amr el-Kahky in Egypt said: "We understand that there were threats if any attempt was made to free these hostages by force - they could be in danger."
German 'crisis team'
Local media quoted Zoheir Garana, the Egyptian tourism minister, on Tuesday as saying that German authorities are negotiating a ransom with the kidnappers of 12 foreign tourists and seven Egyptians.
Garana said his government has not been in contact with the kidnappers, but did not say how he learned of the German negotiations.
Germany's foreign ministry only said it had formed a "crisis team".
Egypt's Middle East News Agency said the ransom demand was as high as $15 million, while Garana said the tour company that organised the safari was negotiating in the range of $6 million.
The safari group was attacked near Gilf al-Kabir region, a sandstone plateau close to the border with Libya and Sudan.
El-Kahky said that five Germans, five Italians, two Romanians and seven Egyptians were a part of the group taken into Sudan by four masked men.
Egyptian officials said the abduction took place on Friday, when the tour leader and owner of the company managed to phone his German wife.
She in turn reported the incident to the authorities.
The tour leader said a group of armed men, who appeared African, drove up to them while they were pitching their tents.
It was not clear when the phone call took place but it was traced to Sudan.
While the incident is not the first time foreign tourists had been targeted in Egypt, it is bad for an economy that heavily depends on tourism. The sector accounts for 11 per cent of the GDP.
"From our point of view, the security of the hostages is the absolute priority - we do not want an operation that harms hostages."