* Ambuehl chief negotiator in U.S. tax talks
* Also leads negotiations with EU over tax
* To step down at the end of August
* May signal Swiss move towards broad tax deals-source
By Oliver Hirt and Caroline Copley
ZURICH, May 24 Switzerland's top tax diplomat will step down at the end of August, the finance ministry said on Friday, as talks with foreign governments eager to crack down on funds hidden in Swiss bank accounts enter a critical phase.
Michael Ambuehl, state secretary for international financial matters since 2010, will take up a job in September at Zurich's Technical University (ETH) as professor of negotiation and conflict management, the ministry said.
Ambuehl has been Switzerland's main negotiator in disputes with tax authorities in the United States and its European neighbours as cash-strapped governments there seek to fill depleted state coffers with a crack down on tax evasion.
Switzerland's long tradition of bank secrecy, which protects the identity of its clients, has seen the country become a haven for untaxed funds.
One source close to the civil service said Ambuehl, who has struck a string of deals with individual countries, did not see eye-to-eye with Finance Minister Eveline Widmer-Schlumpf, and that his departure could be a sign Switzerland is moving towards broader deals that might see it end its opposition to an automatic exchange of information on alleged tax cheats.
"Ambuehl stands for the old Swiss cherry-picking model. For many years Switzerland got a lot out of individual deals with different countries. But this approach doesn't have a future any more. Widmer-Schlumpf stands for multilateral deals and quick results," the source said.
However, a government spokesman denied major friction between the two.
Ambuehl has struck withholding tax deals with Britain and Austria. He is also the chief negotiator in talks to settle a long-running dispute with U.S. tax authorities into Swiss banks, including Credit Suisse and Julius Baer, suspected of helping wealthy Americans evade taxes.
Ambuehl has urged caution over the automatic exchange of data. Widmer-Schlumpf, meanwhile, has hinted Switzerland may have to consider this to end its long-standing tax evasion conflict with the European Union.
EU finance ministers recently gave the go-ahead to start broader talks with Switzerland and other countries about surrendering bank data on an automatic basis.
ON BRINK OF U.S. TAX DEAL
Negotiations with the United States involving about a dozen Swiss banks appear be entering a final phase, with analysts expecting a deal that will involve fines for the banks and a transfer of client names to the U.S. authorities.
Switzerland is also seeking a settlement for the rest of the country's 300 banks.
"We think this doesn't help the talks with the Americans. In this delicate matter continuity is extremely important," said a banker who did not wish to be named.
But a spokesman for the finance minister said Ambuehl would remain head of the department for the next three months, and he would do every thing within his power to advance or close the negotiations.
Rene Matteotti, professor for Swiss, European and international tax law at Zurich university, said one could only speculate about the reasons for Ambuehl's move.
"The change will not impact the tax dispute with the United States as a solution is apparently close at hand," he said.
Talks between the two countries slowed in the middle of last year when Kevin Downing, the U.S. prosecutor most responsible for piercing the veil of Swiss banking secrecy, quit to join a law firm.
Ambuehl is also involved in talks with the EU over changes to Switzerland's corporate tax laws. Brussels has given Switzerland a June 21 deadline to come up with alternatives to special tax breaks on foreign profits if it wants to avoid sanctions.
REFILE-Spanish economy expands at 0.7 pct in Q3 amid political deadlock
MADRID, Oct 28 Spain's economy expanded by 0.7 percent in the July to September period on a quarterly basis, according to preliminary data from the National Statistics Institute (INE) on Friday, a slight slowdown from the previous three months.
BRIEF-Weyerhaeuser reports Q3 earnings of 30 cents a share
* Q3 earnings per share view $0.22 -- Thomson Reuters I/B/E/S