European shares fall as debt woes hit Greek stocks

(Updates prices, adds comment)

* FTSEurofirst 300 down 0.7 pct, Greece's ATG down 5 pct

* FTSEurofirst eyes steepest weekly loss of 2015

* Europe bourses in 2015: http://link.reuters.com/pap87v

By Sudip Kar-Gupta

LONDON, June 5 (Reuters) - European shares dropped on Friday, setting a regional index on course for its steepest weekly fall so far this year as the Athens stock market slid after Greece delayed a debt payment.

Greece's benchmark Athex General Composite (ATG) index tumbled 5.2 percent, underperforming a 0.7 percent decline on the pan-European FTSEurofirst 300 index, which was on track for its biggest weekly decline since December.

Switzerland's Syngenta (Xetra: 580854 - news) was among the worst performers on the FTSEurofirst, retreating 3.3 percent on worries about regulatory hurdles for its deal with U.S. agrochemicals firm Monsanto.

Greece delayed the payment to the International Monetary Fund, due on Friday, as Prime Minister Alexis Tsipras demanded changes to tough terms from international creditors for aid to stave off default.

Economic stimulus measures from the European Central Bank (ECB), coupled with record low interest rates, have cushioned the impact of Greece on European stock markets overall.

Nevertheless, traders viewed the Greek impasse as an opportunity to sell European stocks, many of which have had a good run so far in 2015, with the FTSEurofirst 300 up 12 percent although the Greek market has fallen 5 percent.

"Assurances from Prime Minister Tsipras that Greece will remain in the euro have not exactly soothed investor sentiment today," said London Capital Group's head analyst Brenda Kelly.

U.S. DATA

The lingering uncertainty over Greece's debt problems has come against a volatile market backdrop in which yields on German Bunds rose to eight-month highs earlier this week.

European stock markets also stayed in negative territory after U.S. employment figures were released.

U.S. jobs growth accelerated sharply in May and wages picked up, signs of momentum in the economy that could put a September interest rate hike from the Federal Reserve back on the table.

Non-farm payrolls increased 280,000 last month, the largest gain since December, the Labor Department said on Friday.

Economists polled by Reuters had expected the non-farm payrolls report to show U.S. employers added 225,000 jobs.

Even though the U.S. data pushed up the U.S. dollar against the euro, with a weak euro currency typically benefiting European exporters, traders said worries over Greece meant that the region's stock markets remained under pressure.

"The solid U.S. data could lift the European stock markets, but the central focus remains on Greece which is still unclear and bringing an element of fear to the markets," said ActivTrades chief market analyst Carlo Alberto de Casa.

Asset performance in 2015: http://link.reuters.com/gap87v

Today's European research round-up (Additional reporting by Liisa Tuhkanen and Francesco Canepa; Editing by Mark Heinrich)