Outlook for Swiss industry darkens in September

* Sept PMI at 43.6 pts vs 47.5 pts expected

* Falls for sixth month running

* Level below 50 points indicates contraction

ZURICH, Oct 1 (Reuters) - The outlook for Swiss industry darkened further in September, dragged down by sluggish economies in the euro zone and the United States that central bank actions have so far failed to revive.

The Swiss purchasing managers' index for September fell for the sixth month running to a seasonally adjusted 43.6 points from 46.7 points in the previous month, data showed on Monday. Analysts polled by Reuters had expected a print of 47.5.

The index is compiled by the Swiss SVME purchasing managers' association and Credit Suisse, and a reading below 50 signals a contraction.

"Recent hopes that the two-pronged monetary approach in the U.S. and Europe would result in an early resolution of the debt crisis have not - yet - filtered through to the current PMI survey," the authors said. "On the contrary, the outlook for Swiss industry continued to worsen in September."

The Swiss economy, which earns every second franc abroad, has showed resilience to the euro debt crisis, thanks in part to the cap of 1.20 per euro that the Swiss National Bank set on the local currency just over a year ago.

But it contracted in the second quarter, and economic indicators in addition to the PMI - such as the ZEW investor sentiment index -- paint a cloudy picture.

According to the PMI survey for September, the decline in the backlog of orders accelerated significantly and delivery times shortened.

Market tensions stemming from the euro zone crisis eased last month following the European Central Bank's promise to buy the bonds of some troubled member states. But worries about a Spanish bailout reemerged at the start of October.

The KOF barometer, which points to the economy's expected state in half a year's time, also indicates momentum will wane, though its authors say the economic outlook remains positive.

BACKGROUND For a story on Swiss economy click on... For recent Swiss National Bank comments...

((Zurich newsroom +41.58.306.7336; fax +; zurich.newsroom@reuters.com))

(Editing by John Stonestreet)