By Stephanie Nebehay

GENEVA (Reuters) - Switzerland is trying to help the new authorities of Tunisia, Egypt and Libya recover 770 million Swiss francs ($850 million) in frozen assets linked to their ousted leaders, but the process could take years, a senior Swiss official said on Wednesday.

Separately, the neutral Alpine country, aligning itself with European Union sanctions on Syria, has blocked 45 million francs tied to President Bashar al-Assad and his regime, said Valentin Zellweger, head of international law at the foreign ministry.

The Swiss federal cabinet moved swiftly at the start of the Arab spring in January and February, blocking suspicious funds stashed in Swiss coffers to ensure they were not moved or used to fund Muammar Gaddafi's armed attacks on his people, he said.

Seized assets currently include 300 million francs linked to the deposed Libyan leader, 410 million Swiss francs tied to former Egyptian President Hosni Mubarak, and 60 million francs to former Tunisian President Zine al-Abidine Ben Ali, he said.

Switzerland has already unfrozen 385 million francs and made them available to the new Libyan authorities for the Libyan National Oil Company and Libya Investment Authority, he added.

"The main objective remains quick restitution of funds to Tunisia and Egypt. We are putting all of our efforts into contributing all we can," Zellweger told a news conference.

But 25 years of experience tracing illicit Swiss funds of dictators, including Ferdinand Marcos of the Philippines and Sani Abacha of Nigeria, has shown that lawyers can lodge appeals all the way up to the highest Swiss court, he said.

One-third of the $1.5 billion in assets held offshore by Middle Eastern and African rulers is in Switzerland, some of it illegally obtained, according to the Swiss-based research firm MyPrivateBanking.

Switzerland has tightened money-laundering laws in recent years and requires the country's 7,000 financial institutions to enforce "know your customer" rules, Zellweger said. These also cover so-called "politically-exposed persons" or PEPs, the Swiss term encompassing leaders, ministers and military brass.

"In terms of money restituted globally by all financial centers, of the total 4-5 billion francs estimated by the World Bank, one-third comes from Swiss banks. It's an objective fact, Switzerland is the country that has restituted the most money and this is recognized by a growing number of experts," Zellweger said. "Switzerland is a leader in this domain."

"Swiss banks can of course have relations with 'politically exposed persons'. If Madame (German Chancellor Angela) Merkel came to a bank and asked to open an account, she would be considered a PEP but the bank would have an obligation of due diligence, to review the profile of Madame Merkel regularly."

"ENDEMIC CORRUPTION"

Swiss authorities last week formally accepted a request from Tunisia for judicial assistance in recovering 60 million francs after rejecting the initial request as insufficient.

"Several days ago the Swiss federal justice office accepted the request for assistance from Tunisia. We hope it will bear fruit as quickly as possible. It is an important step that we haven't crossed yet with Egypt, where there is cooperation but for the bulk of its case we're not there yet," Zellweger said.

"Endemic corruption, the Tunisian system that is being discovered now, clearly resembles a certain form of criminal organization, to line the pockets of people in power," he said.

Switzerland has sent financial and legal experts to fledging democracies in North Africa and the Middle East to establish a "relationship of confidence" and help their authorities unlock the web of financial transactions, he said.

"In Tunisia, there have not been many criminal investigations for corruption in the last 30 years. These crimes are enormously complex. Some countries don't have such savoir-faire and it is extremely expensive. It has to be built up," said Zellweger.

(Reporting by Stephanie Nebehay; Editing by Peter Graff)