LONDON, July 23 (Reuters) - Copper prices gained for a fourth straight session on Friday as investors bet that extended easy monetary policy would help to boost economic recovery and metals demand.

Three-month copper on the London Metal Exchange (LME) had climbed 1% to $9,534.50 a tonne by 1615 GMT, on track to finish the week in positive territory.

The European Central Bank pledged on Thursday to keep interest rates at record lows for even longer to boost sluggish inflation.

“In the last few days, the mood among market participants has changed from being quite bearish to very bullish again. I think it’s the continued loose monetary policy of the ECB, and the Fed next week will be even more important,” said analyst Daniel Briesemann at Commerzbank in Frankfurt.

“Demand optimism seems to have regained the upper hand. Just two or three days ago, there were concerns that the rapid spread of the delta variant would hit demand, but this seems to have taken a back seat now.”

Copper, which is used in the power and construction industries among others, is widely viewed as a gauge of global economic health.

LME copper has eased from a record peak of $10,747.50 in May but is still up 22% so far this year. Briesemann expects copper to head lower in coming months to around $8,500.