Egyptian state television on Sunday quoted a presidential decree as saying Mubarak, 76, had delegated his powers to Prime Minister Atif Ubaid during his absence.
"Prime Minister Atif Ubaid will take up temporarily the constitutional and legal powers and jurisdictions of the president of the republic until he returns to take up his duties," state television quoted the presidential decree as saying.
Yasir Rida, the deputy Egyptian ambassador to Berlin, said Mubarak had arrived in Munich and was on his way to the hospital. "Everything is OK," he said. "He is in good shape. It is a routine operation. Nothing serious."
During the operation, scheduled for Monday in Munich, surgeons will insert a microscopic endoscope in Mubarak's lower back to remove displaced cartilage, doctors in Egypt said.
The operation is normally a simple procedure and is expected to last just 40 minutes, but it follows persistent speculation about the health of the Egyptian president who has ruled the Arab world's most populous country since 1981.
Last November he collapsed briefly during a speech to parliament. Officials put that incident down to a combination of cold medication and fasting in the month of Ramadan.
Shroud of secrecy
Concerns about Mubarak's health arose after he postponed meetings this month with Israeli Foreign Minister Silvan Shalom and then with Palestinian Prime Minister Ahmad Quraya.
But he appeared in public last Wednesday, standing and talking to reporters about Egypt's plans to help the Palestinians if and when Israel withdraws from Gaza.
"Everything is OK. He is in good shape. It is a routine operation. Nothing serious"
deputy Egyptian ambassador
A shroud of secrecy about the trip to Germany began to lift on Sunday.
It was initially unclear where the surgery was to be performed and there was also no official announcement on a deputy to run Egypt in his absence until after he arrived.
During previous trips abroad, it was normal practice for Mubarak to delegate some of his powers temporarily to a senior official, usually the prime minister, officials said.
Mubarak has never appointed anyone as a long-term vice president - the route to the presidency in the last two transfers of power in Egypt, in 1970 and 1981.
If he were to die, the speaker of parliament would take over as interim head of state while power brokers decide on a successor to be endorsed by popular referendum.
Egypt's official Middle East News Agency said the operation would take place at Munich Orthopaedics University Hospital.