* Overseas trade top contributor to export rise
* Watches are top gaining sector among exports
* Exports rise by real 2.2 pct y/y in July
ZURICH, Aug 19 (Reuters) - Switzerland's trade surplus rose to a record high in July and exports rose year-on-year, data showed on Thursday, thanks to buoyant overseas markets and in defiance of a stronger currency.
Exports from Switzerland rose by a real 2.2 percent in July to 16.776 billion Swiss francs ($13.32 billion), the Federal Customs Office said. Overall Switzerland ran a merchandise trade surplus of 2.886 billion Swiss francs, its biggest ever, the office said.
The Swiss franc, which investors regard as a safe haven, rallied more than 10 percent against the euro in the first six months of the year, prompting some to caution exports could suffer.
The euro zone is Switzerland's biggest trading partner. Last week data showed Germany's economy grew by 2.2 percent in the second quarter -- its fastest quarterly expansion since reunification. [ID:nLDE67C0AI]
"I expect that in the third quarter things will continue to be strong. If you look at German GDP figures, how exports are booming in Germany, we can expect that Swiss exports will continue to be strong," ZKB economist David Marmet said.
"Most Swiss companies produce technologically sophisticated goods and they have long-term contracts, so the exchange rate doesn't play so much of a role short-term."
The customs office said the rise in exports was chiefly due to extra-European growth. Watches posted a nominal 19.9 percent increase, followed by metals and precision instruments.
Watch exports to Hong Kong, the most important market for Swiss watches, rose 55 percent.
June's trade balance was revised to 1.71 billion francs and exports were revised to 17.254 billion francs.