The eurozone Purchasing Managers' Index (PMI) issued by Reuters suggests that global growth is boosting performance in Europe's factories.

But the strength of the euro remains a concern, along with nervousness among companies that demand will slow.

And a sluggish showing for demand at home for some of Europe's biggest economies is also a concern.

The PMI survey, compiled for Reuters by London-based NTC Research, asks 3,000 companies across the 12-nation eurozone about the state of their business.

In November, the index rose to 52.2, comfortably above the rise-or-fall point of 50 if slightly lower than many economists had forecast.

'Lacklustre'

But it still showed weakness in the shape of falling stocks of finished goods, which usually indicates caution about future prospects, and little progress in cutting unemployment.

The overall picture, said NTC Chief Economist Chris Williamson, was "encouraging but still lacklustre... compared to other major economies around the world, notably the US".

Aside from the strong euro, Mr Williamson warned political factors could be having an effect, with trade and Iraq-related tensions between the US and Europe hitting demand.

Other economists were also worried that the improvement in performance in recent months could prove a flash in the pan.

"With the euro continuing to appreciate and the European Central Bank now likely to adopt a more hawkish stance... following the collapse of the Stability and Growth Pact, we fear that hopes of anything more than a very modest recovery next year could still be dashed," wrote Paul Ashworth, international economist at London-based Capital Economics.

While Europe's big economies, France and Germany, expanded only a fraction of a percentage point in the three months to September, the US grew at a rate which would translate into an annual increase of 8.2%.

The ISM survey of US manufacturing - the broad equivalent of the eurozone PMI - is due out on Monday afternoon, and is expected to show a stronger rise.